North Sea Ecology

Mendonca VM, Raffaelli DG, Boyle PR. 2007. Interactions between shorebirds and benthic invertebrates at Culbin Sands lagoon, NE Scotland: Effects of avian predation on their prey community density and structure. Sci Mar 71(3):579-591.

ABSTRACT: In the North Sea, during autumn-winter, intertidal flats often receive a massive influx of migratory shorebirds (wildfowl, waders and seabirds), which utilise the high prey densities that are available. The present study was conducted at Culbin Sands lagoon, NE Scotland, in 1994-1996, to investigate benthic invertebrate standing stock, and the energy flow from benthic invertebrates to shorebirds. Benthic invertebrate standing stock was estimated to be 500 kJ m-2 yr-1, and shorebird consumption efficiency to be 18% of the available standing stock. A series of manipulative field experiments were then conducted to test the effects of shorebirds on benthic invertebrate densities and community structure. Birds were excluded from caged areas (exclosures), and benthic invertebrate densities (total and by class size) in caged and uncaged areas were compared for each season separately. During autumn-winter, especially the gastropod Hydrobia ulvae and larger-sized (>15 mm) clams Macoma balthica were observed to be the most impacted species, being significantly more abundant in birdexclosures than in bird-accessed areas.

Mendonca VM, Raffaelli DG, Boyle PR, Hoskins S. 2008. Spatial and temporal characteristics of benthic invertebrate communities at Culbin Sands lagoon, Moray Firth, NE Scotland, and impacts of the disturbance of cockle harvesting. Sci Mar 72(2):265-278.

ABSTRACT: In the present study, Culbin Sands lagoon, a protected site in NE Scotland, was surveyed every 2 to 4 weeks during a three-year period (1994-1996) to study benthic invertebrate communities. Beds of Mytilus edulis covered 18000 m2. 53 macroinfaunal species were identified outside these areas. The most conspicuous were: the lugworm Arenicola marina (mean up to 55 casts m-2); and bivalves Cerastoderma edule (mean up to 158 ind. m-2) and Macoma balthica (mean up to 79 ind. m-2) after settlement. The standing stock ranged from 20 to 32 g AFDW m-2 yr-1 respectively from more exposed to more sheltered areas. Most species showed a clear recruitment peak in autumn, but others (e.g. Capitella capitata, and Spionidae) displayed several peaks in a year. Communities were also compared between the sampling sites before and after an incidental disturbance caused by cockle Cerastoderma edule harvesting, which took place in June 1995. One site showed –0.7% variation in the total standing stock, but +22% for smaller-cockles, as larger filter-feeding cockles were removed therefore enhancing their own larval settlement. Polychaete Spionidae populations also increased after larger cockles were removed. The polychaete Arenicola marina population returned to its normal activities just after the dramatic disturbance of the sediment.

"Mendonca VM, Raffaelli DG, Boyle PR, Emes C. 2007. The ecological role of overwintering fish in the food web of the Culbin Sands lagoon ecosystem, NE Scotland: Identifying major trophic links and testing effects of fish Pomatoschistus microps (Pallas) on benthic invertebrates. Sci Mar 71(4):649-660.

ABSTRACT: The Culbin Sands lagoon ecosystem in NE Scotland was studied during a three-year period (1994-1996) to identify the major trophic links from benthic invertebrates to epibenthic predators, and to assess impacts of overwintering fish on their prey communities. Every 2-4 weeks, samples of mobile fauna were collected to study their diets. The major trophic links identified between benthic invertebrates and epibenthic predators were from benthic invertebrates to the shrimp Crangon crangon, and to the common goby Pomatoschistus microps and the plaice Pleuronectes platessa. The energy flow from benthic invertebrates to overwintering fish was estimated at 133 kJ m–2 yr–1. A flow of 10 kJ m–2 yr–1 was also observed from eggs and larval stages of the overwintering shrimp Crangon crangon to the overwintering fish. Nevertheless, manipulative field experiments showed no significant impacts of the most abundant overwintering fish Pomatoschistus microps on prey community densities, despite an overall individual ingestion rate of 89 J day–1.

Mendonca VM, Raffaelli DG, Boyle PR, Emes C. 2009. Trophodynamics in a shallow lagoon off NW Europe (Culbin Sands, Moray Firth): Spatial and temporal variability of epibenthic communities, their diets, and consumption efficiency. Zool Stud 48(2):196-214.

ABSTRACT: Epibenthic communities and their diets, at Culbin Sands (a cold-temperate coastal lagoon in the Moray Firth, northeastern Scotland), were sampled every 2-4 wks for 3 yrs (1994-1996). These communities were more abundant and diverse in warmer months, especially in less-exposed areas of the lagoon. The most common species were the brown shrimp Crangon crangon, the shore crab Carcinus maenas, and teleost fish (sandeel Ammodytes tobianus, sticklebacks Gasterosteus aculeatus and Spinachia spinachia, seascorpion Myoxocephalus scorpius, gobies Pomatoschistus microps and Pomatoschistus minutus, flounder Platichthys flesus, and plaice Pleuronectes platessa). Diets of these epibenthic predators included benthic infauna (especially polychaetes Eteone longa, Pygospio elegans, and Fabricia sabella; oligochaetes Tubificoides benedini; isopods Eurydice pulchra; and bivalves Cerastoderma edule and Macoma balthica), small epibenthic organisms (amphipods especially Bathyporeia pilosa and Gammarus sp., and juvenile crabs Carcinus maenas and shrimp Crangon crangon), and zooplankton (harpacticoids, ostracods mostly Cypris sp., calanoid copepods, mysids Praunus flexuosus, and fish eggs and larvae). Insect larvae (Chironomidae) were also common in the stomach contents of the epibenthic predators. In fact, prey items with higher indices of relative importance for the most abundant predators (brown shrimp, common gobies, and plaice) were insect larvae for shrimp, amphipods Bathyporeia pilosa for shrimp and gobies, harpacticoids for plaice and gobies, and bivalves (larvae and siphons of adult individuals) mostly for plaice. Brown shrimp, common goby, and plaice had daily consumption levels of 1%, 3%, and 2.5% of their own body wet weights, respectively. Energy flows of 150, 68, and 65 kJ m-2 yr-1 were estimated from benthic invertebrates to brown shrimp, common gobies, and plaice, equivalent to consumption efficiencies of 30%, 15%, and 15%, respectively, of the standing stock of benthic invertebrates and small epibenthic species such as amphipods.