Effects of Temperature, Salinity and Fish in Structuring the Macroinvertebrate Community in Shallow Lakes: Implications for Effects of Climate Change

Abstract

Climate warming may lead to changes in the trophic structure and diversity of shallow lakes as a combined effect of increased temperature and salinity and likely increased strength of trophic interactions. We investigated the potential effects of temperature, salinity and fish on the plant-associated macroinvertebrate community by introducing artificial plants in eight comparable shallow brackish lakes located in two climatic regions of contrasting temperature: cold-temperate and Mediterranean. In both regions, lakes covered a salinity gradient from freshwater to oligohaline waters. We undertook day and night-time sampling of macroinvertebrates associated with the artificial plants and fish and free-swimming macroinvertebrate predators within artificial plants and in pelagic areas. Our results showed marked differences in the trophic structure between cold and warm shallow lakes. Plant-associated macroinvertebrates and free-swimming macroinvertebrate predators were more abundant and the communities richer in species in the cold compared to the warm climate, most probably as a result of differences in fish predation pressure. Submerged plants in warm brackish lakes did not seem to counteract the effect of fish predation on macroinvertebrates to the same extent as in temperate freshwater lakes, since small fish were abundant and tended to aggregate within the macrophytes. The richness and abundance of most plant-associated macroinvertebrate taxa decreased with salinity. Despite the lower densities of plant-associated macroinvertebrates in the Mediterranean lakes, periphyton biomass was lower than in cold temperate systems, a fact that was mainly attributed to grazing and disturbance by fish. Our results suggest that, if the current process of warming entails higher chances of shallow lakes becoming warmer and more saline, climatic change may result in a decrease in macroinvertebrate species richness and abundance in shallow lakes.

Outcomes of submerged macrophyte restoration in a shallow impounded, eutrophic river

“…Larger cladocerans, which exert more grazing pressure on phytoplankton (Brooks and Dodson, 1965), were rarely found in high abundance. This is consistent with studies in subtropical waters where high densities of small omnivorous fish prevent development of large cladoceran populations (Beklioglu et al, 2007;Brucet et al, 2012). Macrophyte meadows in our study had high abundance of predatory invertebrates (Coenagrionidae, Notonectidae, Corixidae) and the omnivorous G. holbrooki.…”

“…This result is not surprising, with vegetated aquatic systems known to support much greater biomass and diversity of invertebrates (Dvorak and Best, 1982;Heck and Crowder, 1991). However, while fish communities within macrophytes may limit macroinvetebrate populations in some shallow subtropical systems (Brucet et al, 2012), this was not observed in our study. Plant structure and associated increased surface area and niche diversity may offer greater potential for…”

Ecological impacts of global warming and water abstraction on lakes and reservoirs due to changes in water level and related changes in salinity

“…Global warming reinforces the eutrophication of already eutrophic lakes (Moss et al, 2011), with significant changes in lake food web structure and community composition Meerhoff et al, 2007;Brucet et al, 2010;Jeppesen et al, 2010a, b;Brucet et al, 2012;Meerhoff et al, 2012), and causes higher proportions of cyanobacteria in summer (Wagner & Adrian, 2009;Kosten et al, 2012). In the Mediterranean climate zone and other areas with semi-arid desert climates, changes in water level, hydraulic retention time and salinity associated with warming may have considerable further effects on lake ecosystem structure and dynamics (reviews by Wantzen et al, 2008, andBrucet et al, 2010;Zohary & Ostrovsky, 2011;Brucet et al, 2012).…”

“…In the Mediterranean climate zone and other areas with semi-arid desert climates, changes in water level, hydraulic retention time and salinity associated with warming may have considerable further effects on lake ecosystem structure and dynamics (reviews by Wantzen et al, 2008, andBrucet et al, 2010;Zohary & Ostrovsky, 2011;Brucet et al, 2012). Besides nutrient loading, evaporative up-concentration of nutrients in reduced water volumes becomes an additional factor enhancing eutrophication under warmer conditions (Ö zen et al, 2010), and longer water residence time may favour the rowth and blooming of cyanobacteria, especially the toxin-producing ones such as Microcystis spp.…”

Aquatic invertebrate assemblages in ponds from coastal Mediterranean wetlands

“…Conductivity may also influence the macroinvertebrate distribution, since malacostraceans are more tolerant to high salt concentrations (Piscart et al, 2005;Boix et al, 2008). In addition, macroinvertebrate assemblages in brackish warm lakes are poorer than in temperate regions, especially free-swimming invertebrates, probably due to the higher predation pressure (Brucet et al, 2012). However, the malacostracean species, found mainly in the ponds with fish, are faster swimmers and have benthic behavior, so they could reduce the influence of fish predation near the sediment or among vegetation.…”