Benthic algal biomass – measurement and errors.

Journal of Plankton Research, 2004

Assessment of the contribution of distinct algal groups to phytoplankton biomass in oligotrophic lakes by marker pigments is compared with assessment by cell-counting biovolume estimates. Seasonal samples from an oligotrophic alpine lake (Redon, Pyrenees) mostly included species of chrysophytes, dinoflagellates, cryptophytes and chlorophytes. The chlorophyl a (Chl a) corresponding to each algal group was estimated using HPLC pigment analyses and the CHEMTAX program. Chl a estimates and biovolume showed a significant correlation for all the groups during the ice-free season except for chlorophytes. However, some of the samples from the initial phase of the ice cover presented a clear departure from the relationship during the ice-free period in most groups. On the other hand, the ratios between a specific marker pigment and the biovolume of the marked algal group were significantly constant within the photic zone (>1% surface irradiance) for most of the pigments and groups, including chlorophytes. Nevertheless, the ratios increased and showed a large variability for samples below the photic depth or below the ice cover. The violaxanthin-chrysophyte biovolume ratio presented an opposed tendency to other pigment-biovolume ratios, which increased in inverse proportion to the depth of the sample. The results are discussed in terms of methodological limitations, acclimation responses and species composition.

Canadian Journal of Fisheries and Aquatic Sciences, 2003

We quantified the chlorophyll a content of planktonic algae and benthic algae in periphyton on acrylic rods and in epiphyton growing on macrophytes in 24 coastal wetlands in all five Laurentian Great Lakes. Sites were selected to represent a wide range of environmental conditions ranging from nutrient-poor, clear-water marshes with abundant macrophytes to nutrient-enriched, turbid systems devoid of aquatic vegetation. Water quality and species and percent cover of submergent macrophytes were measured in each wetland. Principal components analysis (PCA) showed that total phosphorus, turbidity, and suspended solids, variables associated with human-induced degradation, were most strongly correlated with PC axis 1 (PC1), accounting for 69% of the total variation. The PC1 site score was significantly related to both periphyton and phytoplankton biomass, respectively accounting for 54 and 70% of the total variation in periphyton and phytoplankton data, whereas PC1 only accounted for 18% of the variation in epiphyton biomass. Periphytic and epiphytic biomass were negatively correlated with percent cover and species richness of submergent macrophytes, but phytoplankton biomass was not. We conclude that periphytic and planktonic chlorophyll a biomass are good indicators of human-induced water-quality degradation and recommend that both benthic and planktonic algal biomass should be routinely monitored as part of an effective wetland management program.

International Journal of Environmental Protection, 2011

The mesotrophic Ikizcetepeler Reservoir was sampled monthly from February 2007 to June 2008 at three stations. Thermal stratification occurred in the reservoir from May to September. The results revealed high bands of chlorophyll in the epilimnion and metalimnion of the reservoir during summer and winter. Results suggest that high chlorophyll accumulation was a result of the increase in available light levels in spring and deep mixing, providing phytoplankton with the nutrients needed for grow in summer. Correlation analyses were used to determine the relationships between chlorophyll (µg/L), water temperature (o Nutrient concentrations can be used to determine which nutrient may be limiting to algal growth [6]. However, it is difficult to interpret the results when different taxa have different cellular N:P ratios and require different optimal environmental conditions [7]. Therefore, using N:P ratios might be a better way of interpreting nutrient limitation on algal growth [8]. Jappesen et al. [9] state that at low N: P ratios, phytoplankton community composition shiftes towards a dominance of N-fixing Cyanobacteria. Low N:P could create conditions that greatly benefit N-fixing cyanobacteria, which are able to outcompete other phytoplankton by importing considerable amounts of N from the atmosphere [10]. Thus, without a commensurate decrease in other nutrients, especially P, programmes that seek to improve water quality by reducing N loading may actually deteriorate water quality in freshwater ecosystems. Wang et al. [11] argue that the TN:TP ratio is not inappropriate to be used as an index to discriminate lakes as N or P-limited because for a multi-species community, optimal N:P ratios vary greatly among phytoplankton species. Also, the effects of grazing by zooplankton could significantlty affect the dynamics of phytoplankton biomass over time and space. C), total nitrogen (mg/L), total phosphorus (mg/L) and Secchi disk depth (m). Differences in chlorophyll, total phosphorus, total nitrogen and in Secchi disk transparency were not significant among sampling stations (p>0.01), but they were significant among seasons (p<0.01). Successful control of eutrophication requires an understanding of how nutrients, physical conditions and biological processes interact to affect algal growth and since the utility of chlorophyll in estimating algal biomass worldwide , this study was conducted to determine how variations in water temperature, total nitrogen, total phosphorus and water transparency affected the the vertical and seasonal distribution of chlorophyll in Ikizcetepeler Reservoir.

Ecosphere, 2011

Internationale …, 2008

Aquatic Sciences, 2010

The factors affecting vertical distributions of chlorophyll fluorescence were examined in four temperate, warm monomictic lakes. Each of the lakes (maximum depth [80 m) was sampled over 2 years at intervals from monthly to seasonal. Profiles were taken of chlorophyll fluorescence (as a proxy for algal biomass), temperature and irradiance, as well as integrated samples from the surface mixed layer for chlorophyll a (chl a) and nutrient concentrations in each lake. Depth profiles of chlorophyll fluorescence were also made along transects of the longest axis of each lake. Chlorophyll fluorescence maxima occurred at depths closely correlated with euphotic depth (r 2 = 0.67, P \ 0.01), which varied with nutrient status of the lakes. While seasonal thermal density stratification is a prerequisite for the existence of a deep chlorophyll maximum (DCM), our study provides evidence that the depth of light penetration largely dictates the DCM depth during stratification. Reduction in water clarity through eutrophication can cause a shift in phytoplankton distributions from a DCM in spring or summer to a surface chlorophyll maximum within the surface mixed layer when the depth of the euphotic zone (z eu ) is consistently shallower than the depth of the surface mixed layer (z SML ). Trophic status has a key role in determining vertical distributions of chlorophyll in the four lakes, but does not appear to disrupt the annual cycle of maximum chlorophyll in winter.

Biologia, 2006

Using image analysis, chlorophyll autofluorescence was measured in single cells of green alga Monoraphidium dybowskii and in filaments of cyanobacteria (Pseudanabaena sp. and Limnothrix sp.) in the vertical profile of small acidified mountain lake Plešné jezero (Plešné Lake) from May to November of 2003. Cell chlorophyll autofluorescence was converted to cell chlorophyll content using a conversion factor determined by comparing the total autofluorescence of phytoplankton in a microscope field with spectrophotometrically determined total chlorophyll concentration; the conversion factor did not differ between epilimnion (0.5 m depth) and hypolimnion (9 m depth). Vertical patterns of chlorophyll concentration and of cellular chlorophyll content depended on water column mixing: during the period of stable thermal stratification, a metalimnetic peak in total chlorophyll concentration was present and cellular chlorophyll contents in the metalimnion and hypolimnion were notably elevated compared to the surface. Monotonous vertical profiles of both total chlorophyll concentration and cell chlorophyll content were typical for the period of water column overturn. During the stratification period, hypolimnetic Monoraphidium cell chlorophyll content was on average twice as high (maximum difference 2.7-fold) compared to surface values (of 3.2-12.9 fg µm −3 ), while in filamentous cyanobacteria (surface cell chlorophyll content of 2.2-13.3 fg µm −3 ), the difference was much higher -six-fold on average, with an 11.6-fold maximum value. The values measured with image analysis in 2003 were compared to unpublished values of total phytoplankton biomass-specific chlorophyll concentrations obtained using manual phytoplankton biomass determination and spectrophotometric chlorophyll measurement in 1998 at the same locality. Good agreement was found in seasonal patterns and vertical profiles of chlorophyll between both seasons.

Freshwater Biology, 1995

1. Oligotrophic Lake Waikaremoana, New Zealand, is used for hydroelectric power generation and the lake levels are manipulated within an operating range of 3 m. There was concern that rapidly changing water levels adversely affected the littoral zone by decreasing Ught availability in two ways: local turbidity caused by shoreline erosion at low water levels; and decreased light penetration to the deep littoral zone caused by high water levels in summer. 2. The littoral zone was dominated by native aquatic plants with vascular species to 6 m and a characean n:\eadow below this to 16 m. The biomass and heights of the communities in the depth zone 0-6 m were reduced at a site exposed to wave action relative to those at a sheltered site. However, the community structure below 6 m was similar at exposed and sheltered sites. The lower boundary of the littoral zone was sharply delimited at 16 m and this bottom boundary remained constant throughout the year despite large seasonal changes in solar radiation and the 3 m variation in lake level. 3. There was evidence that the deep-water community consisting of Chara coralUna had adapted physiologically to low-light conditions. Net light saturated photosynthesis (CO, exchange) per unit chlorophyll a (Chi a) was reduced to 1.7 (jig C (p.g Chi a) ' h' at the lower boundary, half of that recorded at 5 m. The concentration of Chi a per gram of biomass (dry weight), was considerably greater at the lower boundary than higher in the profile [c. 7 mg Chi a (g dry wt)-' at 16 m vs. 4 mg Chi a (g dry wt)-' at 5 m]. Chi b also increased with depth and there was no change in the ratio of Chi a and Chi b with increasing depth. The saturation light intensity (/^) of the community at the lower boundary was only 78 pmol photons m-^ s'. Photosynthetic parameters (J^ and a) as well as the Chi a content remained relatively constant throughout the seasonal and short-term changes in radiation. 4. The photosynthetic characteristics of the littoral commimity were therefore not greatly affected by the lake level change caused by the present hydroelectric operations. However, the sharpness of the lower boundary and its extreme shade characteristics imply that the deep-water community would be sensitive to any further changes in imdenvater light availability. zone' devoid of littoral vegetation which defines upper

Canadian Journal of Fisheries and Aquatic Sciences, 2009

Primary production, planktonic respiration, bacterial abundance, and chlorophyll a were measured in the epilimnion of two Canadian Shield lakes and in two large rivers to establish their metabolic balance and to contrast oligotrophic and oligo-mesotrophic systems. Pronounced diel respiration cycles were observed in all systems, with a minimum in the morning and a maximum in the evening. Respiration was positively correlated with water temperature, incident light, and chlorophyll a concentration. Diel cycles of chlorophyll a were discernible in both rivers and in the oligo-mesotrophic lake. Our results show that a single morning sampling underestimates both respiration and chlorophyll a, whereas a single sample taken at noon generally agrees better with the average of four daily measurements. In oligotrophic Lac Croche, the photosynthetic parameter a B remained constant throughout the day, whereas P m B increased by 12.5% between 0600 h and 1300 h. Ignoring the diel community respiration cycle resulted in a~25% underestimation of daily respiration, whereas ignoring the P m B cycle induced a~9% underestimation of the daily primary production. The net balance between production (P) and respiration (R) of the oligotrophic lake epilimnion remained positive during two summers, and the P:R ratio showed net autotrophy for all systems except for the oligotrophic river, which was slightly net heterotrophic.