Omnivorous Carp (Carassius gibelio) Increase Eutrophication in Part by Preventing Development of Large-Bodied Zooplankton and Submerged Macrophytes

Vladimir Razlutskij,Andrei Makaranka,Elena Sysova,Erik Jeppesen,Xueying Mei,Dzmitry Lukashanets,Xiufeng Zhang,Natallia Maisak

doi:10.3390/w13111497

Abstract

Fish, being an important consumer in aquatic ecosystems, plays a significant role by affecting the key processes of aquatic ecosystems. Omnivorous fish consume a variety of food both from pelagic and benthic habitats and may directly or indirectly affect the plankton community as well as the lake trophic state. We conducted a 72-day outdoor experiment in mesocosms with and without Prussian carp (Carassius auratus) to evaluate the effect of this often-stocked omnivorous fish on the plankton community and water quality. We found that the presence of fish increased the biomass of planktonic algae, total and inorganic suspended solids, leading to decreased light intensity in the water and a lower biomass of benthic algae. Fish also prevented development of submerged macrophytes and the establishment of large-bodied zooplankton. However, the fish did not increase nitrogen concentrations and even was lowered total phosphorus levels, in part due to nutrient storage in the fish. We conclude that stocking of Prussian carp should be avoided, or removed where stocked and abundant, to obtain good ecological quality of shallow lakes, characterized by clear water and high abundance of macrophytes.

Highlights

Eutrophication due to excess nutrient inputs, leading to extensive growth of planktonic algae, is one of the most common water quality problems in shallow lakes worldwide [1,2,3].When abundant, planktonic algae reduce water transparency and prevent penetration of light into deeper layers, which, in turn, may reduce the growth of benthic primary producers such as benthic algae [4,5,6]
A decrease in benthic primary production may result in higher growth of planktonic algae through reduced competition for nutrients and enhanced internal nutrient loading from the sediment [7]
Filtering fish such as silver carp (Hypophthalmichthys molitrix) filter plankton and particles in the water column and is supposed to have a positive effect on water quality [12], this view is controversial as they consume the zooplankton, thereby reducing the grazing on planktonic algae [13]. Other fish, such as common carp (Cyprinus carpio) consume a variety of food items from both the pelagic and benthic habitats, and they may have profound effects on the aquatic ecosystems [14,15]. They affect nutrient recycling and primary productivity in aquatic ecosystems, either directly or indirectly [16,17]: they may enhance the growth of planktonic algae through bottom-up effects by translocating nutrients from sediments to the water column [18,19,20] as well as by disturbance and through excretion [8,21]

Summary

Introduction

Eutrophication due to excess nutrient inputs, leading to extensive growth of planktonic algae, is one of the most common water quality problems in shallow lakes worldwide [1,2,3].When abundant, planktonic algae reduce water transparency and prevent penetration of light into deeper layers, which, in turn, may reduce the growth of benthic primary producers such as benthic algae [4,5,6]. Filtering fish such as silver carp (Hypophthalmichthys molitrix) filter plankton and particles in the water column and is supposed to have a positive effect on water quality [12], this view is controversial as they consume the zooplankton, thereby reducing the grazing on planktonic algae [13] Other fish, such as common carp (Cyprinus carpio) consume a variety of food items from both the pelagic and benthic habitats, and they may have profound effects on the aquatic ecosystems [14,15]. Omnivorous fish can predate on phytoplankton-consuming zooplankton, thereby reducing their abundance and changing their community structure [22,23,24] They may, increase turbidity through resuspension of bottom sediments when feeding [25,26,27], potentially with negative effect on primary producers. The impact of fish on nutrient concentrations and water turbidity varied with season and latitude in a

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Conclusion