We examined the ability of seagrasses to take up dissolved organic nitrogen (DON) with leaves (in... more We examined the ability of seagrasses to take up dissolved organic nitrogen (DON) with leaves (in situ) and roots (laboratory) in an oligotrophic tropical offshore meadow in Indonesia using $^{{\rm{15}}} {\rm{N}}$-labeled nitrogen (N) substrates. We compared the uptake of urea and amino acids with that of ammonium $({\rm{NH}}_{\rm{4}}^{\rm{ + }})$ and nitrate $({\rm{NO}}_{\rm{3}}^{\rm{ - }})$ and determined uptake kinetics of
A revolution in plant modeling in the 1970s highlighted the need for better respiration algorithm... more A revolution in plant modeling in the 1970s highlighted the need for better respiration algorithms. Subsequent research enhanced conceptual insights into processes underlying growth and maintenance respiration. This chapter offers an overview of the most important basic concepts used to partition respiration into energy-utilizing components for growth, maintenance and ion uptake, both with respect to modeling and for experimental measurements.
We explored to what extent morphological variation and habitat modification are correlated for an... more We explored to what extent morphological variation and habitat modification are correlated for an autogenic ecosystem engineer, which is an organism that modifies its habitat via its own physical structures. The intertidal salt marsh speciesSpartina anglica is well known for its capacity to enhance sediment accretion within its canopy by reducing hydrodynamic energy. Sediment accretion is favorable toSpartina, as it
Although knowledge on dispersal patterns is essential for predicting long-term population dynamic... more Although knowledge on dispersal patterns is essential for predicting long-term population dynamics, critical information on the modalities of passive dispersal and potential interactions between vectors is often missing. Here, we use mangrove propagules with a wide variety of morphologies to investigate the interaction between water and wind as a driver of passive dispersal. We imposed 16 combinations of wind and hydrodynamic conditions in a flume tank, using propagules of six important mangrove species (and genera), resulting in a set of dispersal morphologies that covers most variation present in mangrove propagules worldwide. Additionally, we discussed the broader implications of the outcome of this flume study on the potential of long distance dispersal for mangrove propagules in nature, applying a conceptual model to a natural mangrove system in Gazi Bay (Kenya). Overall, the effect of wind on dispersal depended on propagule density (g l -1 ). The low-density Heritiera littoralis propagules were most affected by wind, while the high-density vertically floating propagules of Ceriops tagal and Bruguiera gymnorrhiza were least affected. Avicennia marina, and horizontally floating Rhizophora mucronata and C. tagal propagules behaved similarly. Morphological propagule traits, such as the dorsal sail of H. littoralis, explained another part of the interspecific differences. Within species, differences in dispersal velocities can be explained by differences in density and for H. littoralis also by variations in the shape of the dorsal sail. Our conceptual model illustrates that different propagule types have a different likelihood of reaching the open ocean depending on prevailing water and wind currents. Results suggest that in open water, propagule traits (density, morphology, and floating orientation) appear to determine the effect of water and wind currents on dispersal dynamics. This has important implications for inter-and intraspecific variation in dispersal patterns and the likelihood of reaching suitable habitat patches within a propagule's viable period.
Coastal systems are increasingly threatened by multiple local anthropogenic and global climatic s... more Coastal systems are increasingly threatened by multiple local anthropogenic and global climatic stressors. With the difficulties in remediating global stressors, management requires alternative approaches that focus on local scales. We used manipulative experiments to test whether reducing local stressors (sediment load and nutrient concentrations) can improve the resilience of foundation species (canopy algae along temperate rocky coastlines) to future projected global climate stressors (high wave exposure, increasing sea surface temperature), which are less amenable to management actions. We focused on Fucoids (Cystoseira barbata) along the north-western Adriatic coast in the Mediterranean Sea because of their ecological relevance, sensitivity to a variety of human impacts, and declared conservation priority. At current levels of sediment and nutrients, C. barbata showed negative responses to the simulated future scenarios of high wave exposure and increased sea surface temperature. However, reducing the sediment load increased the survival of C. barbata recruits by 90.24% at high wave exposure while reducing nutrient concentrations resulted in a 20.14% increase in the survival and enhanced the growth of recruited juveniles at high temperature. We conclude that improving water quality by reducing nutrient concentrations, and particularly the sediment load, would significantly increase the resilience of C. barbata populations to projected increases in climate stressors. Developing and applying appropriate targets for specific local anthropogenic stressors could be an effective management action to halt the severe and ongoing loss of key marine habitats.
Seagrass beds are highly productive coastal ecosystems providing a large array of ecosystem servi... more Seagrass beds are highly productive coastal ecosystems providing a large array of ecosystem services including fisheries and carbon sequestration. As seagrasses are known to be highly sensitive to anthropogenic forcing, we evaluated the use of trace metal concentrations in seagrasses as bioindicators for trace metal pollution of coastal regions at both global and local scale. We carried out a meta-analysis based on literature data to provide a global benchmark list for trace metal accumulation in seagrasses, which was lacking in literature. We subsequently carried out a case study at the Caribbean islands of Curaçao and Bonaire to test for local-scale differences in trace metal concentrations in seagrasses, and internal metal allocation. The benchmark and local study show that trace metal concentrations in seagrass leaves, regardless of the species, can vary over a 100-1000-fold range, and are related to the level of anthropogenic pressure, making seagrasses highly valuable indicators.
... 2005; Mazda et al. 1995). ... Elsevier, pp. 333-357. Barbier, EB, EW Koch, BR Silliman, SDHac... more ... 2005; Mazda et al. 1995). ... Elsevier, pp. 333-357. Barbier, EB, EW Koch, BR Silliman, SDHacker, E. Wolanski, J. Primavera, EF Granek, S. Polasky, S. Aswani, LA Cramer, DM Stoms, CJ Kennedy, D. Bael, CV Kappel, GME Perillo and DJ Reed. 2008. ...
Little information is available on the variability of the dynamics of the actual and observed roo... more Little information is available on the variability of the dynamics of the actual and observed root respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil CO 2 concentration, temperature, soil water content and root respiration, and II) the effect of short-term fluctuations of these three environmental factors on the relation between actual and observed root respiration rates. We designed an automated, open, gasexchange system that allows continuous measurements on 12 chambers with intact roots in soil. By using three distinct chamber designs with each a different path for the air flow, we were able to measure root respiration over a 50-fold range of soil CO 2 concentrations (400 to 25000 ppm) and to separate the effect of irrigation on observed vs. actual root respiration rate. All respiration measurements were made on one-year-old citrus seedlings in sterilized sandy soil with minimal organic material.
The relation between root age and root function is poorly understood, despite its importance to r... more The relation between root age and root function is poorly understood, despite its importance to root longevity. • The effect of root age on respiration rates and 32 P-uptake kinetics was determined for roots excavated from mature apple and citrus trees (median root life spans of 30 vs 300 d). To evaluate whether root longevity maximizes the efficiency of nutrient capture, daily and lifetime efficiencies were calculated by dividing simulated P-uptake benefits (solute transport model) by age-specific respiration costs. • We found that: respiration rates and P uptake capacity change with root age in a species-specific way; and soil characteristics that determine the rate of nutrient depletion in the rhizosphere are as important as changes in root physiology in determining the age at which a root reaches its maximum efficiency. • Further testing of the efficiency of nutrient capture as a predictor of root life span requires measurement of both soil properties and age-specific physiology of roots including their mycorrhizal fungi.
We compared the root systems of seven halophytic species that occur at different elevations on a ... more We compared the root systems of seven halophytic species that occur at different elevations on a salt marsh, in order to (i) test the hypothesis that variations in root system architecture reflect adaptation to inundation frequency or nitrogen limitation, and (ii) verify the theoretically predicted relationships between root diameter, link magnitude and root topology. Diameters and lengths of individual laterals were determined along root axes, and branching patterns were quantified by calculating a topological index (TI). 2. Chenopodiaceae (annual dicots) showed that with increasing elevation, the branch density and length of individual first-order laterals tended to increase, so that the relative length of the main axes decreased. Root branching of the Chenopodiaceae at lower elevations was herringbone-like, whereas species from higher elevations had smaller TIs because their branching patterns were more complex. 3. The Gramineae, too, showed a tendency to increased length of individual laterals with increasing elevation. However, TI was not related to elevation, did not indicate a herringbone structure for all species, and was within the same range of that of the Chenopodiaceae. 4. As root topology of the Chenopodiaceae is related to elevation, but that of the grasses is not, topology is not necessarily an important adaptive trait in all plant families that inhabit the salt marsh. Short first-and second-order laterals may represent a more general architectural adaptation to frequent inundation, with longer first-order laterals being favourable to competition for nutrients. 5. Diameters at the root base tended to decrease if root branching was herringbone-like (TI close to 1). Roots of first-order laterals were approximately one-third of the diameter of the main axes; second-order laterals were approximately half the diameter of the firstorder laterals. These ratios illustrate the value of using the developmental segment-ordering system in describing roots. The theoretically predicted relationship between root diameter and link magnitude was not present within individual orders of roots, whereas diameter did slowly increase with magnitude when combining different root orders. 6. In the absence of a clear relationship between root diameter and link magnitude, the predicted high carbon costs associated with herringbone root systems disappear, whereas the advantage of minimized inter-root competition remains. Consequently, herringbone root systems will be most efficient in terms of nutrients gained per carbon invested. However, dichotomous root systems offer a greater potential for exploring the soil, which contributes to the potential competitiveness of plants growing in nutrient limited habitats.
Seagrass beds are globally declining due to human activities in coastal areas. We here aimed to i... more Seagrass beds are globally declining due to human activities in coastal areas. We here aimed to identify threats from eutrophication to the valuable seagrass beds of Curaçao and Bonaire in the Caribbean, which function as nursery habitats for commercial fish species. We documented surface- and porewater nutrient concentrations, and seagrass nutrient concentrations in 6 bays varying in nutrient loads. Water measurements only provided a momentary snapshot, due to timing, tidal stage, etc., but Thalassia testudinum nutrient concentrations indicated long-term nutrient loads. Nutrient levels in most bays did not raise any concern, but high leaf % P values of Thalassia in Piscadera Bay (∼0.31%) and Spanish Water Bay (∼0.21%) showed that seagrasses may be threatened by eutrophication, due to emergency overflow of waste water and coastal housing. We thus showed that seagrasses may be threatened and measures should be taken to prevent loss of these important nursery areas due to eutrophication.
As a result of anthropogenic disturbances and natural stressors, seagrass beds are often patchy a... more As a result of anthropogenic disturbances and natural stressors, seagrass beds are often patchy and heterogeneous. The effects of high loads of nutrients and organic matter in patch development and expansion in heterogeneous seagrass beds have, however, poorly been studied. We experimentally assessed the in situ effects of sediment quality on seagrass (Zostera noltii) patch dynamics by studying patch (0.35 m diameter) development and expansion for 4 sediment treatments: control, nutrient addition (NPK), organic matter addition (OM) and a combination (NPK + OM). OM addition strongly increased porewater sulfide concentrations whereas NPK increased porewater ammonium, nitrate and phosphate concentrations. As high nitrate concentrations suppressed sulfide production in NPK + OM, this treatment was biogeochemically comparable to NPK. Sulfide and ammonium concentrations differed within treatments, but over a 77 days period, seagrass patch survival and expansion were impaired by all additions compared to the control treatment. Expansion decreased at porewater ammonium concentrations >2000 mol L −1 . Mother patch biomass was not affected by high porewater ammonium concentrations as a result of its detoxification by higher seagrass densities. Sulfide concentrations >1000 mol L −1 were toxic to both patch expansion and mother patch. We conclude that patch survival and expansion are constrained at high loads of nutrients or organic matter as a result of porewater ammonium or sulfide toxicity.
Despite being a highly valuable key-stone ecosystem, seagrass meadows are threatened and declinin... more Despite being a highly valuable key-stone ecosystem, seagrass meadows are threatened and declining worldwide, creating urgent need for indicators of their health status. We compared two indicators for seagrass health: standing leaf area index versus relative recovery from local disturbance. Disturbance was created by removing aboveground biomass and recording the rate of regrowth for Zostera marina meadows exposed to contrasting wave regimes and nutrient stress levels. Within the experimental period, relative regrowth in gaps was around 50% in most plots, except for the ambient nutrient treatment at the sheltered site, where it exceeded 100%. The two indicators showed an opposite response to disturbance: the higher the standing leaf area index, the lower the relative recovery from disturbance. This conflicting response raises the question on the proper interpretation of such indicators to estimate seagrass health and resilience, and how to ideally monitor seagrass ecosystems in orde...
Mangroves thrive in sheltered intertidal areas in the tropics and sub-tropics. Due to this positi... more Mangroves thrive in sheltered intertidal areas in the tropics and sub-tropics. Due to this position at the interface between land and sea, mangroves play an important role in the attenuation of waves. Dissipation of wave energy in mangrove forests is an interesting feature from the viewpoint of coastal protection. Nevertheless, field data are sparse and modeling attempts reveal the need for additional data. This paper presents the results of an extensive field campaign, lasting 6 months, in mangroves along the Andaman coast of Trang Province in southern Thailand. Wave attenuation has been studied along two contrasting transects with different elevation and vegetation characteristics and different orientations towards the Andaman Sea. Along the Kantang transect, which is mostly exposed to swell waves, vegetation densities increased from 4.5 to 9.3 volume-‰ along the transect and on average 63% of the incident wave energy was attenuated over a distance of 246 m. Along the Palian transect, mostly exposed to sea waves instead, vegetation increased from 4.3 to 19 volume-‰ and 72% of the incident wave energy was attenuated over this 98 m transect. It was found that standardized wave attenuation correlates well with incident wave energy, when attenuation is analyzed per vegetation zone. Energy reduction rates of these zones, defined by the gradient of the correlations between the standardized wave attenuation and incident wave energy, are found to increase significantly with vegetation density. Consistently, wave reduction rates, expressing the gradient of the correlation between wave height reduction and incident wave heights, are found to be 0.001-0.014 for the study sites and also show a significant and increasing trend with vegetation densities.
Ecosystems in the tropical coastal zone exchange particulate organic matter (POM) with adjacent s... more Ecosystems in the tropical coastal zone exchange particulate organic matter (POM) with adjacent systems, but differences in this function among ecosystems remain poorly quantified. Seagrass beds are often a relatively small section of this coastal zone, but have a potentially much larger ecological influence than suggested by their surface area. Using stable isotopes as tracers of oceanic, terrestrial, mangrove and seagrass sources, we investigated the origin of particulate organic matter in nine mangrove bays around the island of Phuket (Thailand). We used a linear mixing model based on bulk organic carbon, total nitrogen and δ13C and δ15N and found that oceanic sources dominated suspended particulate organic matter samples along the mangrove-seagrass-ocean gradient. Sediment trap samples showed contributions from four sources oceanic, mangrove forest/terrestrial and seagrass beds where oceanic had the strongest contribution and seagrass beds the smallest. Based on ecosystem area, ...
Seagrasses are generally known as ecosystem engineers, as they reduce flow velocities in their ca... more Seagrasses are generally known as ecosystem engineers, as they reduce flow velocities in their canopies. In perennial subtidal meadows, this usually leads to increased net sedimentation rates and reduction of the grain size. The present study aims to describe the contribution of annual seagrass populations to these processes and elucidate the temporal dynamics. Sediment accretion and grain size modification were
Human infrastructures can modify ecosystems, thereby affecting the occurrence and spatial distrib... more Human infrastructures can modify ecosystems, thereby affecting the occurrence and spatial distribution of organisms, as well as ecosystem functionality. Sustainable development requires the ability to predict responses of species to anthropogenic pressures. We investigated the large scale, long term effect of important human alterations of benthic habitats with an integrated approach combining engineering and ecological modelling. We focused our analysis on the Oosterschelde basin (The Netherlands), which was partially embanked by a storm surge barrier (Oosterscheldekering, 1986). We made use of 1) a prognostic (numerical) environmental (hydrodynamic) model and 2) a novel application of quantile regression to Species Distribution Modeling (SDM) to simulate both the realized and potential (habitat suitability) abundance of four macrozoobenthic species: Scoloplos armiger, Peringia ulvae, Cerastoderma edule and Lanice conchilega. The analysis shows that part of the fluctuations in macrozoobenthic biomass stocks during the last decades is related to the effect of the coastal defense infrastructures on the basin morphology and hydrodynamics. The methodological framework we propose is particularly suitable for the analysis of large abundance datasets combined with high-resolution environmental data. Our analysis provides useful information on future changes in ecosystem functionality induced by human activities. Citation: Cozzoli F, Eelkema M, Bouma TJ, Ysebaert T, Escaravage V, et al. (2014) A Mixed Modeling Approach to Predict the Effect of Environmental Modification on Species Distributions. PLoS ONE 9(2): e89131.
Physical habitat complexity regulates the structure and function of biological communities, altho... more Physical habitat complexity regulates the structure and function of biological communities, although the mechanisms underlying this relationship remain unclear. Urbanisation, pollution, unsustainable resource exploitation and climate change have resulted in the widespread simplification (and loss) of habitats worldwide. One way to restore physical complexity to anthropogenically simplified habitats is through the use of artificial substrates, which also offer excellent opportunities to explore the effects of different components (variables) of complexity on biodiversity and community structure that would be difficult to separate in natural systems. Here, we describe a software program (CASU) that enables users to visualise static, physical complexity. CASU also provides output files that can be used to create artificial substrates for experimental and/or restoration studies. It has two different operational modes: simple and advanced. In simple mode, users can adjust the five main variables of informational complexity (i.e. the number of object types, relative abundance of object types, density of objects, variability and range in the objects' dimensions, and their spatial arrangement) and visualise the changes as they do so. The advanced mode allows users to design artificial substrates by fine-tuning the complexity variables as well as alter object-specific parameters. We illustrate how CASU can be used to create tiles of different designs for application in a marine environment. Such an ability to systematically influence physical complexity could greatly facilitate ecological restoration by allowing conservationists to rebuild complexity in degraded and simplified habitats.
Abbreviations -AOP, alternative oxidase pathway; AOX, alternative oxidase; ATP, adenosine triphos... more Abbreviations -AOP, alternative oxidase pathway; AOX, alternative oxidase; ATP, adenosine triphosphate; COP, cytochrome oxidase pathway; Da, oxygen-isotope fractionation by alternative pathway; Dc, oxygen-isotope fractionation by cytochrome pathway; Dn, oxygen-isotope fractionation in the absence of inhibitors; g R , specific costs of tissue construction; g Ralt , specific costs of tissue construction provided by the alternative pathway respiration; g RATP , specific costs of tissue construction (mmol ATP g growth 21 ); g Rcyt , specific costs of tissue construction provided by the cytochrome pathway respiration; g Roxy , specific costs of tissue construction (mmol O 2 g growth 21 ); m R , specific costs of tissue maintenance; m Ralt , specific costs of tissue maintenance provided by alternative pathway respiration; m RATP , specific costs of tissue maintenance (nmol ATP g 21 s 21 ); m Rcyt , specific costs of tissue maintenance provided by cytochrome pathway respiration; m Roxy , specific costs of tissue maintenance (nmol O 2 g 21 s 21 ); P GR , respiration efficiency coefficient for the specific costs for growth; P MR , respiration efficiency coefficient for the specific costs for maintenance; r, total respiration; r alt , alternative pathway respiration; r ATP , overall tissue respiration (nmol ATP g 21 s 21 ); r cyt , cytochrome pathway respiration; RGR, relative growth rate; r oxy , overall tissue respiration (nmol O 2 g 21 s 21 ); SE, standard error; SHAM, salicylhydroxamic acid; t a , the electron partitioning through the alternative pathway; v alt , activity of the alternative oxidase pathway; v cyt , activity of the cytochrome oxidase pathway; V t , total oxygen uptake rate.
There is an extremely limited understanding of how plants of different potential growth rate vary... more There is an extremely limited understanding of how plants of different potential growth rate vary in root traits, especially in woody species. We contrasted fine root morphology, physiology, and elemental construction between a fast-and a slow-growing species in each of three families: Aceraceae (maple), Fagaceae (oak), and Pinaceae (pine). Measurements were primarily made on 1-year-old seedlings growing in a growth chamber. Across all three families, first-and second-order roots of fast-growing species had greater specific root length, thinner diameters, and faster respiration rates than those of slow-growing species. These fine roots of fast-growing species in Aceraceae and Fagaceae also had faster phosphorus (P) uptake on a surface area basis than those of slow-growing species, whereas little difference in P uptake was found between Pinaceae species. On a dry weight basis, roots of fast-growing species in Aceraceae and Fagaceae had higher nitrogen concentrations, lower carbon:nitrogen ratios and higher tissue construction costs than roots of slow-growing species (data were unavailable for Pinaceae). Tissue density did not vary in a consistent pattern between fast-and slow-growing species across all three families (P=0.169). To better understand the ecological significance of differences in these root characteristics, a root efficiency model was used to compare P uptake and root carbon (C) cost of each species in simulated field situations in two soils, one with low P buffering capacity (loamy sand) and another with relatively high P buffering capacity (silt loam). For the soil conditions modeled, fast-growing species of Aceraceae and Fagaceae were 17-70% more efficient (defined as cumulative P gain divided by cumulative C cost) at nutrient capture than slow-growing species while the fastgrowing Pinaceae species was 20-24% less efficient than the slow-growing species. However, among all three families, roots of fast-growing species reached maximum lifetime efficiency 5-120 days sooner, depending on soil type. Thus, modeling results indicated that root traits of fast-and slow-growing species affected P acquisition in simulated field soil although soil type also had a strong impact.
We examined the ability of seagrasses to take up dissolved organic nitrogen (DON) with leaves (in... more We examined the ability of seagrasses to take up dissolved organic nitrogen (DON) with leaves (in situ) and roots (laboratory) in an oligotrophic tropical offshore meadow in Indonesia using $^{{\rm{15}}} {\rm{N}}$-labeled nitrogen (N) substrates. We compared the uptake of urea and amino acids with that of ammonium $({\rm{NH}}_{\rm{4}}^{\rm{ + }})$ and nitrate $({\rm{NO}}_{\rm{3}}^{\rm{ - }})$ and determined uptake kinetics of
A revolution in plant modeling in the 1970s highlighted the need for better respiration algorithm... more A revolution in plant modeling in the 1970s highlighted the need for better respiration algorithms. Subsequent research enhanced conceptual insights into processes underlying growth and maintenance respiration. This chapter offers an overview of the most important basic concepts used to partition respiration into energy-utilizing components for growth, maintenance and ion uptake, both with respect to modeling and for experimental measurements.
We explored to what extent morphological variation and habitat modification are correlated for an... more We explored to what extent morphological variation and habitat modification are correlated for an autogenic ecosystem engineer, which is an organism that modifies its habitat via its own physical structures. The intertidal salt marsh speciesSpartina anglica is well known for its capacity to enhance sediment accretion within its canopy by reducing hydrodynamic energy. Sediment accretion is favorable toSpartina, as it
Although knowledge on dispersal patterns is essential for predicting long-term population dynamic... more Although knowledge on dispersal patterns is essential for predicting long-term population dynamics, critical information on the modalities of passive dispersal and potential interactions between vectors is often missing. Here, we use mangrove propagules with a wide variety of morphologies to investigate the interaction between water and wind as a driver of passive dispersal. We imposed 16 combinations of wind and hydrodynamic conditions in a flume tank, using propagules of six important mangrove species (and genera), resulting in a set of dispersal morphologies that covers most variation present in mangrove propagules worldwide. Additionally, we discussed the broader implications of the outcome of this flume study on the potential of long distance dispersal for mangrove propagules in nature, applying a conceptual model to a natural mangrove system in Gazi Bay (Kenya). Overall, the effect of wind on dispersal depended on propagule density (g l -1 ). The low-density Heritiera littoralis propagules were most affected by wind, while the high-density vertically floating propagules of Ceriops tagal and Bruguiera gymnorrhiza were least affected. Avicennia marina, and horizontally floating Rhizophora mucronata and C. tagal propagules behaved similarly. Morphological propagule traits, such as the dorsal sail of H. littoralis, explained another part of the interspecific differences. Within species, differences in dispersal velocities can be explained by differences in density and for H. littoralis also by variations in the shape of the dorsal sail. Our conceptual model illustrates that different propagule types have a different likelihood of reaching the open ocean depending on prevailing water and wind currents. Results suggest that in open water, propagule traits (density, morphology, and floating orientation) appear to determine the effect of water and wind currents on dispersal dynamics. This has important implications for inter-and intraspecific variation in dispersal patterns and the likelihood of reaching suitable habitat patches within a propagule's viable period.
Coastal systems are increasingly threatened by multiple local anthropogenic and global climatic s... more Coastal systems are increasingly threatened by multiple local anthropogenic and global climatic stressors. With the difficulties in remediating global stressors, management requires alternative approaches that focus on local scales. We used manipulative experiments to test whether reducing local stressors (sediment load and nutrient concentrations) can improve the resilience of foundation species (canopy algae along temperate rocky coastlines) to future projected global climate stressors (high wave exposure, increasing sea surface temperature), which are less amenable to management actions. We focused on Fucoids (Cystoseira barbata) along the north-western Adriatic coast in the Mediterranean Sea because of their ecological relevance, sensitivity to a variety of human impacts, and declared conservation priority. At current levels of sediment and nutrients, C. barbata showed negative responses to the simulated future scenarios of high wave exposure and increased sea surface temperature. However, reducing the sediment load increased the survival of C. barbata recruits by 90.24% at high wave exposure while reducing nutrient concentrations resulted in a 20.14% increase in the survival and enhanced the growth of recruited juveniles at high temperature. We conclude that improving water quality by reducing nutrient concentrations, and particularly the sediment load, would significantly increase the resilience of C. barbata populations to projected increases in climate stressors. Developing and applying appropriate targets for specific local anthropogenic stressors could be an effective management action to halt the severe and ongoing loss of key marine habitats.
Seagrass beds are highly productive coastal ecosystems providing a large array of ecosystem servi... more Seagrass beds are highly productive coastal ecosystems providing a large array of ecosystem services including fisheries and carbon sequestration. As seagrasses are known to be highly sensitive to anthropogenic forcing, we evaluated the use of trace metal concentrations in seagrasses as bioindicators for trace metal pollution of coastal regions at both global and local scale. We carried out a meta-analysis based on literature data to provide a global benchmark list for trace metal accumulation in seagrasses, which was lacking in literature. We subsequently carried out a case study at the Caribbean islands of Curaçao and Bonaire to test for local-scale differences in trace metal concentrations in seagrasses, and internal metal allocation. The benchmark and local study show that trace metal concentrations in seagrass leaves, regardless of the species, can vary over a 100-1000-fold range, and are related to the level of anthropogenic pressure, making seagrasses highly valuable indicators.
... 2005; Mazda et al. 1995). ... Elsevier, pp. 333-357. Barbier, EB, EW Koch, BR Silliman, SDHac... more ... 2005; Mazda et al. 1995). ... Elsevier, pp. 333-357. Barbier, EB, EW Koch, BR Silliman, SDHacker, E. Wolanski, J. Primavera, EF Granek, S. Polasky, S. Aswani, LA Cramer, DM Stoms, CJ Kennedy, D. Bael, CV Kappel, GME Perillo and DJ Reed. 2008. ...
Little information is available on the variability of the dynamics of the actual and observed roo... more Little information is available on the variability of the dynamics of the actual and observed root respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil CO 2 concentration, temperature, soil water content and root respiration, and II) the effect of short-term fluctuations of these three environmental factors on the relation between actual and observed root respiration rates. We designed an automated, open, gasexchange system that allows continuous measurements on 12 chambers with intact roots in soil. By using three distinct chamber designs with each a different path for the air flow, we were able to measure root respiration over a 50-fold range of soil CO 2 concentrations (400 to 25000 ppm) and to separate the effect of irrigation on observed vs. actual root respiration rate. All respiration measurements were made on one-year-old citrus seedlings in sterilized sandy soil with minimal organic material.
The relation between root age and root function is poorly understood, despite its importance to r... more The relation between root age and root function is poorly understood, despite its importance to root longevity. • The effect of root age on respiration rates and 32 P-uptake kinetics was determined for roots excavated from mature apple and citrus trees (median root life spans of 30 vs 300 d). To evaluate whether root longevity maximizes the efficiency of nutrient capture, daily and lifetime efficiencies were calculated by dividing simulated P-uptake benefits (solute transport model) by age-specific respiration costs. • We found that: respiration rates and P uptake capacity change with root age in a species-specific way; and soil characteristics that determine the rate of nutrient depletion in the rhizosphere are as important as changes in root physiology in determining the age at which a root reaches its maximum efficiency. • Further testing of the efficiency of nutrient capture as a predictor of root life span requires measurement of both soil properties and age-specific physiology of roots including their mycorrhizal fungi.
We compared the root systems of seven halophytic species that occur at different elevations on a ... more We compared the root systems of seven halophytic species that occur at different elevations on a salt marsh, in order to (i) test the hypothesis that variations in root system architecture reflect adaptation to inundation frequency or nitrogen limitation, and (ii) verify the theoretically predicted relationships between root diameter, link magnitude and root topology. Diameters and lengths of individual laterals were determined along root axes, and branching patterns were quantified by calculating a topological index (TI). 2. Chenopodiaceae (annual dicots) showed that with increasing elevation, the branch density and length of individual first-order laterals tended to increase, so that the relative length of the main axes decreased. Root branching of the Chenopodiaceae at lower elevations was herringbone-like, whereas species from higher elevations had smaller TIs because their branching patterns were more complex. 3. The Gramineae, too, showed a tendency to increased length of individual laterals with increasing elevation. However, TI was not related to elevation, did not indicate a herringbone structure for all species, and was within the same range of that of the Chenopodiaceae. 4. As root topology of the Chenopodiaceae is related to elevation, but that of the grasses is not, topology is not necessarily an important adaptive trait in all plant families that inhabit the salt marsh. Short first-and second-order laterals may represent a more general architectural adaptation to frequent inundation, with longer first-order laterals being favourable to competition for nutrients. 5. Diameters at the root base tended to decrease if root branching was herringbone-like (TI close to 1). Roots of first-order laterals were approximately one-third of the diameter of the main axes; second-order laterals were approximately half the diameter of the firstorder laterals. These ratios illustrate the value of using the developmental segment-ordering system in describing roots. The theoretically predicted relationship between root diameter and link magnitude was not present within individual orders of roots, whereas diameter did slowly increase with magnitude when combining different root orders. 6. In the absence of a clear relationship between root diameter and link magnitude, the predicted high carbon costs associated with herringbone root systems disappear, whereas the advantage of minimized inter-root competition remains. Consequently, herringbone root systems will be most efficient in terms of nutrients gained per carbon invested. However, dichotomous root systems offer a greater potential for exploring the soil, which contributes to the potential competitiveness of plants growing in nutrient limited habitats.
Seagrass beds are globally declining due to human activities in coastal areas. We here aimed to i... more Seagrass beds are globally declining due to human activities in coastal areas. We here aimed to identify threats from eutrophication to the valuable seagrass beds of Curaçao and Bonaire in the Caribbean, which function as nursery habitats for commercial fish species. We documented surface- and porewater nutrient concentrations, and seagrass nutrient concentrations in 6 bays varying in nutrient loads. Water measurements only provided a momentary snapshot, due to timing, tidal stage, etc., but Thalassia testudinum nutrient concentrations indicated long-term nutrient loads. Nutrient levels in most bays did not raise any concern, but high leaf % P values of Thalassia in Piscadera Bay (∼0.31%) and Spanish Water Bay (∼0.21%) showed that seagrasses may be threatened by eutrophication, due to emergency overflow of waste water and coastal housing. We thus showed that seagrasses may be threatened and measures should be taken to prevent loss of these important nursery areas due to eutrophication.
As a result of anthropogenic disturbances and natural stressors, seagrass beds are often patchy a... more As a result of anthropogenic disturbances and natural stressors, seagrass beds are often patchy and heterogeneous. The effects of high loads of nutrients and organic matter in patch development and expansion in heterogeneous seagrass beds have, however, poorly been studied. We experimentally assessed the in situ effects of sediment quality on seagrass (Zostera noltii) patch dynamics by studying patch (0.35 m diameter) development and expansion for 4 sediment treatments: control, nutrient addition (NPK), organic matter addition (OM) and a combination (NPK + OM). OM addition strongly increased porewater sulfide concentrations whereas NPK increased porewater ammonium, nitrate and phosphate concentrations. As high nitrate concentrations suppressed sulfide production in NPK + OM, this treatment was biogeochemically comparable to NPK. Sulfide and ammonium concentrations differed within treatments, but over a 77 days period, seagrass patch survival and expansion were impaired by all additions compared to the control treatment. Expansion decreased at porewater ammonium concentrations >2000 mol L −1 . Mother patch biomass was not affected by high porewater ammonium concentrations as a result of its detoxification by higher seagrass densities. Sulfide concentrations >1000 mol L −1 were toxic to both patch expansion and mother patch. We conclude that patch survival and expansion are constrained at high loads of nutrients or organic matter as a result of porewater ammonium or sulfide toxicity.
Despite being a highly valuable key-stone ecosystem, seagrass meadows are threatened and declinin... more Despite being a highly valuable key-stone ecosystem, seagrass meadows are threatened and declining worldwide, creating urgent need for indicators of their health status. We compared two indicators for seagrass health: standing leaf area index versus relative recovery from local disturbance. Disturbance was created by removing aboveground biomass and recording the rate of regrowth for Zostera marina meadows exposed to contrasting wave regimes and nutrient stress levels. Within the experimental period, relative regrowth in gaps was around 50% in most plots, except for the ambient nutrient treatment at the sheltered site, where it exceeded 100%. The two indicators showed an opposite response to disturbance: the higher the standing leaf area index, the lower the relative recovery from disturbance. This conflicting response raises the question on the proper interpretation of such indicators to estimate seagrass health and resilience, and how to ideally monitor seagrass ecosystems in orde...
Mangroves thrive in sheltered intertidal areas in the tropics and sub-tropics. Due to this positi... more Mangroves thrive in sheltered intertidal areas in the tropics and sub-tropics. Due to this position at the interface between land and sea, mangroves play an important role in the attenuation of waves. Dissipation of wave energy in mangrove forests is an interesting feature from the viewpoint of coastal protection. Nevertheless, field data are sparse and modeling attempts reveal the need for additional data. This paper presents the results of an extensive field campaign, lasting 6 months, in mangroves along the Andaman coast of Trang Province in southern Thailand. Wave attenuation has been studied along two contrasting transects with different elevation and vegetation characteristics and different orientations towards the Andaman Sea. Along the Kantang transect, which is mostly exposed to swell waves, vegetation densities increased from 4.5 to 9.3 volume-‰ along the transect and on average 63% of the incident wave energy was attenuated over a distance of 246 m. Along the Palian transect, mostly exposed to sea waves instead, vegetation increased from 4.3 to 19 volume-‰ and 72% of the incident wave energy was attenuated over this 98 m transect. It was found that standardized wave attenuation correlates well with incident wave energy, when attenuation is analyzed per vegetation zone. Energy reduction rates of these zones, defined by the gradient of the correlations between the standardized wave attenuation and incident wave energy, are found to increase significantly with vegetation density. Consistently, wave reduction rates, expressing the gradient of the correlation between wave height reduction and incident wave heights, are found to be 0.001-0.014 for the study sites and also show a significant and increasing trend with vegetation densities.
Ecosystems in the tropical coastal zone exchange particulate organic matter (POM) with adjacent s... more Ecosystems in the tropical coastal zone exchange particulate organic matter (POM) with adjacent systems, but differences in this function among ecosystems remain poorly quantified. Seagrass beds are often a relatively small section of this coastal zone, but have a potentially much larger ecological influence than suggested by their surface area. Using stable isotopes as tracers of oceanic, terrestrial, mangrove and seagrass sources, we investigated the origin of particulate organic matter in nine mangrove bays around the island of Phuket (Thailand). We used a linear mixing model based on bulk organic carbon, total nitrogen and δ13C and δ15N and found that oceanic sources dominated suspended particulate organic matter samples along the mangrove-seagrass-ocean gradient. Sediment trap samples showed contributions from four sources oceanic, mangrove forest/terrestrial and seagrass beds where oceanic had the strongest contribution and seagrass beds the smallest. Based on ecosystem area, ...
Seagrasses are generally known as ecosystem engineers, as they reduce flow velocities in their ca... more Seagrasses are generally known as ecosystem engineers, as they reduce flow velocities in their canopies. In perennial subtidal meadows, this usually leads to increased net sedimentation rates and reduction of the grain size. The present study aims to describe the contribution of annual seagrass populations to these processes and elucidate the temporal dynamics. Sediment accretion and grain size modification were
Human infrastructures can modify ecosystems, thereby affecting the occurrence and spatial distrib... more Human infrastructures can modify ecosystems, thereby affecting the occurrence and spatial distribution of organisms, as well as ecosystem functionality. Sustainable development requires the ability to predict responses of species to anthropogenic pressures. We investigated the large scale, long term effect of important human alterations of benthic habitats with an integrated approach combining engineering and ecological modelling. We focused our analysis on the Oosterschelde basin (The Netherlands), which was partially embanked by a storm surge barrier (Oosterscheldekering, 1986). We made use of 1) a prognostic (numerical) environmental (hydrodynamic) model and 2) a novel application of quantile regression to Species Distribution Modeling (SDM) to simulate both the realized and potential (habitat suitability) abundance of four macrozoobenthic species: Scoloplos armiger, Peringia ulvae, Cerastoderma edule and Lanice conchilega. The analysis shows that part of the fluctuations in macrozoobenthic biomass stocks during the last decades is related to the effect of the coastal defense infrastructures on the basin morphology and hydrodynamics. The methodological framework we propose is particularly suitable for the analysis of large abundance datasets combined with high-resolution environmental data. Our analysis provides useful information on future changes in ecosystem functionality induced by human activities. Citation: Cozzoli F, Eelkema M, Bouma TJ, Ysebaert T, Escaravage V, et al. (2014) A Mixed Modeling Approach to Predict the Effect of Environmental Modification on Species Distributions. PLoS ONE 9(2): e89131.
Physical habitat complexity regulates the structure and function of biological communities, altho... more Physical habitat complexity regulates the structure and function of biological communities, although the mechanisms underlying this relationship remain unclear. Urbanisation, pollution, unsustainable resource exploitation and climate change have resulted in the widespread simplification (and loss) of habitats worldwide. One way to restore physical complexity to anthropogenically simplified habitats is through the use of artificial substrates, which also offer excellent opportunities to explore the effects of different components (variables) of complexity on biodiversity and community structure that would be difficult to separate in natural systems. Here, we describe a software program (CASU) that enables users to visualise static, physical complexity. CASU also provides output files that can be used to create artificial substrates for experimental and/or restoration studies. It has two different operational modes: simple and advanced. In simple mode, users can adjust the five main variables of informational complexity (i.e. the number of object types, relative abundance of object types, density of objects, variability and range in the objects' dimensions, and their spatial arrangement) and visualise the changes as they do so. The advanced mode allows users to design artificial substrates by fine-tuning the complexity variables as well as alter object-specific parameters. We illustrate how CASU can be used to create tiles of different designs for application in a marine environment. Such an ability to systematically influence physical complexity could greatly facilitate ecological restoration by allowing conservationists to rebuild complexity in degraded and simplified habitats.
Abbreviations -AOP, alternative oxidase pathway; AOX, alternative oxidase; ATP, adenosine triphos... more Abbreviations -AOP, alternative oxidase pathway; AOX, alternative oxidase; ATP, adenosine triphosphate; COP, cytochrome oxidase pathway; Da, oxygen-isotope fractionation by alternative pathway; Dc, oxygen-isotope fractionation by cytochrome pathway; Dn, oxygen-isotope fractionation in the absence of inhibitors; g R , specific costs of tissue construction; g Ralt , specific costs of tissue construction provided by the alternative pathway respiration; g RATP , specific costs of tissue construction (mmol ATP g growth 21 ); g Rcyt , specific costs of tissue construction provided by the cytochrome pathway respiration; g Roxy , specific costs of tissue construction (mmol O 2 g growth 21 ); m R , specific costs of tissue maintenance; m Ralt , specific costs of tissue maintenance provided by alternative pathway respiration; m RATP , specific costs of tissue maintenance (nmol ATP g 21 s 21 ); m Rcyt , specific costs of tissue maintenance provided by cytochrome pathway respiration; m Roxy , specific costs of tissue maintenance (nmol O 2 g 21 s 21 ); P GR , respiration efficiency coefficient for the specific costs for growth; P MR , respiration efficiency coefficient for the specific costs for maintenance; r, total respiration; r alt , alternative pathway respiration; r ATP , overall tissue respiration (nmol ATP g 21 s 21 ); r cyt , cytochrome pathway respiration; RGR, relative growth rate; r oxy , overall tissue respiration (nmol O 2 g 21 s 21 ); SE, standard error; SHAM, salicylhydroxamic acid; t a , the electron partitioning through the alternative pathway; v alt , activity of the alternative oxidase pathway; v cyt , activity of the cytochrome oxidase pathway; V t , total oxygen uptake rate.
There is an extremely limited understanding of how plants of different potential growth rate vary... more There is an extremely limited understanding of how plants of different potential growth rate vary in root traits, especially in woody species. We contrasted fine root morphology, physiology, and elemental construction between a fast-and a slow-growing species in each of three families: Aceraceae (maple), Fagaceae (oak), and Pinaceae (pine). Measurements were primarily made on 1-year-old seedlings growing in a growth chamber. Across all three families, first-and second-order roots of fast-growing species had greater specific root length, thinner diameters, and faster respiration rates than those of slow-growing species. These fine roots of fast-growing species in Aceraceae and Fagaceae also had faster phosphorus (P) uptake on a surface area basis than those of slow-growing species, whereas little difference in P uptake was found between Pinaceae species. On a dry weight basis, roots of fast-growing species in Aceraceae and Fagaceae had higher nitrogen concentrations, lower carbon:nitrogen ratios and higher tissue construction costs than roots of slow-growing species (data were unavailable for Pinaceae). Tissue density did not vary in a consistent pattern between fast-and slow-growing species across all three families (P=0.169). To better understand the ecological significance of differences in these root characteristics, a root efficiency model was used to compare P uptake and root carbon (C) cost of each species in simulated field situations in two soils, one with low P buffering capacity (loamy sand) and another with relatively high P buffering capacity (silt loam). For the soil conditions modeled, fast-growing species of Aceraceae and Fagaceae were 17-70% more efficient (defined as cumulative P gain divided by cumulative C cost) at nutrient capture than slow-growing species while the fastgrowing Pinaceae species was 20-24% less efficient than the slow-growing species. However, among all three families, roots of fast-growing species reached maximum lifetime efficiency 5-120 days sooner, depending on soil type. Thus, modeling results indicated that root traits of fast-and slow-growing species affected P acquisition in simulated field soil although soil type also had a strong impact.
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Papers by Tjeerd Bouma