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Title:	Grazing effects of alien amphipods on macroalgae in the littoral zone of the Neva Estuary (eastern Gulf of Finland, Baltic Sea)
Authors:	Berezina Nadezhda Golubkov Sergey Gubelit Julia
Abstract:	It is hypothesized that the alien amphipods Gmelinoides fasciatus and Pontogammarus robustoides, which have recently invaded the eastern Gulf of Finland, are able to control macroalgae biomass. In order to test this, studies were conducted on the seasonal dynamics of amphipod populations and filamentous algae, Cladophora glomerata, in the Neva Estuary in 2003. The absolute abundance of the gammarids ranged from 200 to 4800 ind.m^-2 with the maximum in June and July. The biomass of Cladophora increased from June to August, reaching 1.7-2.0 kgm^-2 wet weight. Gut content analysis revealed that both gammarid species are omnivorous; however, P. robustoides grazed more successfully on C. glomerata than did G. fasciatus. The proportion of the algae in the P. robustoides diet depended on consumer body length prevailing in the diets of middle-sized (7.5–12.0 mm) specimens. The evaluation of the condition of P. robustoides fed different diets indicated that with the Cladophora diet, the clutch size was the largest but the growth rate was the lowest. The growth rate was the highest on the mixed diet (algae and animals at a weight ratio of 1:1), which indicated that this diet was the optimal feeding strategy for consumer fitness. The data obtained clearly indicated that the grazing amphipods, P. robustoides, can have a dramatic impact on C. glomerata in the littoral zone of the eastern Gulf of Finland and perhaps control the macroalgal biomass when populations are dense.
DOI:
Type of paper:	Original research paper
Pages:	63 to 82
Cytation:	Berezina N., Golubkov S., Gubelit J., 2005, Grazing effects of alien amphipods on macroalgae in the littoral zone of the Neva Estuary (eastern Gulf of Finland, Baltic Sea), Ocean. Hydrob. Studies, 34(Supl. 1): 63-82
Keywords:	Pontagammarus robustoides, Gmelinoides fasciatus, feeding, grazing activity, growth rates, fecundity
Year:	2005
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