scholarly journals The Effect of Salinity and Nutrient Load on the Ecosystems of Selected Lakes in the South of Siberia

2021 ◽  
pp. 154-167
Author(s):  
Egor S. Zadereev
Keyword(s):  
Food Web ◽  
Trophic Levels ◽  
Trophic Chain ◽  
General Description ◽  
Nutrient Load ◽  
Key Factors ◽  
Lake Ecosystems ◽  
Food Web Interactions ◽  
South Of Siberia ◽  
Diverse Community

Salinity largely determines the species diversity and structure of the food web in lake ecosystems. Many studies have been focused on the salinity tolerance of various plankton species. There are fewer studies investigating the modifications in the food web interactions under the effect of salinity. An appropriate system for such studies is closely located lakes of different salinity. We took samples during the summer stratification and analyzed the physicochemical and biological characteristics of 20 lakes (salinity 0.1-35 g/l) in southern Siberia in order to provide general description of this system and to test a number of hypotheses about the effect of salinity on the structure of the food web. The analysis revealed two key factors structuring ecosystems of the studied lakes. The species composition of zooplankton was determined by salinity, with a decrease in the number of species and the transformation of the community from a diverse community of zooplankton (salinity up to 3 g/l) to the dominance of large daphnia (3-8 g/l), copepods (> 8 g/l), small cladocerans and rotifers (20-30 g/l), and Artemia (> 30 g/l). The top predator (fish) was eliminated at salinity above 10 g/l. The biomass of zooplankton did not depend on salinity, but significantly increased in lakes with an increased nutrient load. The nutrient load also had a significant effect on the concentration of total phosphorus, turbidity and transparency of water, and the concentration of chlorophyll “a”. Thus, we recorded the structuring effect of the nutrient load (bottom-up control) on the biomass of the trophic levels and the parameters of water transparency, while salinity transformed the trophic chain from the top, leading to the disappearance of fish and a change in the dominant species of zooplankton. At the same time, salinity did not affect the biomass of the trophic levels. In order to detect top-down effects in the ecosystems of saline lakes, it is necessary to perform a comparative analysis of the seasonal dynamics of ecosystems of lakes with different salinity

scholarly journals Beyond the fish-Daphnia paradigm: testing the potential for Neoplea striola (Hemiptera: Pleidae) to cause a trophic cascade in subtropical ponds

2021 ◽  
Author(s):  
Chase J. Rakowski ◽  
Mathew A. Leibold
Keyword(s):  
Food Web ◽  
Trophic Cascade ◽  
Trophic Cascades ◽  
Zooplankton Community ◽  
Trophic Levels ◽  
Food Web Interactions ◽  
Top Predators ◽  
Invertebrate Predators ◽  
Consumption Rates ◽  
Central Texas

AbstractTrophic cascades, or indirect effects of predators on non-adjacent lower trophic levels, are thought to pervade diverse ecosystems, though they tend to be stronger in aquatic ecosystems. Most research on freshwater trophic cascades focused on temperate lakes where Daphnia tend to dominate the zooplankton community, and these studies identified that Daphnia plays a key role in facilitating trophic cascades by linking fish to algae with strong food web interactions. However, Daphnia are rare or absent in most tropical and subtropical lowland freshwaters, and many invertebrate predators have received little attention in food web research despite being common and widespread. Therefore, we aimed to test whether trophic cascades are possible in small warmwater ponds where small invertebrates are the top predators and Daphnia are absent. We collected naturally occurring plankton communities from small fishless water bodies in central Texas and propagated them in replicate pond mesocosms. We removed zooplankton from some mesocosms, left the plankton community intact in others, and added one of two densities of the predaceous insect Neoplea striola to others. Following an incubation period we then compared biomasses of plankton groups to assess food web effects between the trophic levels including whether Neoplea caused a trophic cascade by reducing zooplankton. The zooplankton community became dominated by copepods which prefer large phytoplankton and exhibit a fast escape response. Perhaps due to these qualities of the copepods and perhaps due to slow consumption rates by Neoplea on key grazers, no food web effects were found other than zooplankton marginally reducing large phytoplankton. More research is needed to understand the behavior and ecology of Neoplea, but trophic cascades may generally be weak or absent in subtropical and tropical lowland freshwaters where Daphnia is rare.

scholarly journals Primary Sources and Food Web Structure of a Tropical Wetland with High Density of Mangrove Forest

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3105
Author(s):  
Victor M. Muro-Torres ◽  
Felipe Amezcua ◽  
Martin Soto-Jiménez ◽  
Eduardo F. Balart ◽  
Elisa Serviere-Zaragoza ◽  
...  
Keyword(s):  
Food Web ◽  
Gulf Of California ◽  
Trophic Ecology ◽  
Abundant Species ◽  
Trophic Levels ◽  
Isotopic Niche ◽  
Trophic Chain ◽  
Mangrove Forests ◽  
Food Web Structure ◽  
Wide Range

The trophic ecology of wetlands with mangrove forests remains poorly understood. Through the use of stomach contents analysis, stable isotope signatures, and Bayesian mixing models, the food web of a tropical wetland in the gulf of California was investigated. Consumers had heterogeneous diets, omnivores were the most abundant species (47%), followed by planktivorous (21%), minor piscivores (10%), major piscivores (10%), macrobenthivores (9%), and herbivores (3%). The values of δ13C (from −12 to −29‰) and δ15N (from 4 to 24‰) showed a wide range of isotopic values of the consumers. Most of the species had a broad isotopic niche and there was a large diet overlap of species due to the exploitation of a common set of food resources. Five trophic levels were identified, with the weakfish (Cynoscion xanthulus) as the top predator of this system with detritus coming from the mangrove as the main source that supports the food chain. This highlights the importance of the mangrove forests to such ecosystems, because not only they are the most important primary food source, but also, they offer habitat to a large suite of fauna, which are important components of the trophic chain.

Introduction

2017 ◽  
Author(s):  
Christer Brönmark ◽  
Lars-Anders Hansson
Keyword(s):  
Food Web ◽  
Natural Ecosystems ◽  
Environmental Threats ◽  
Food Web Interactions

The chapter introduces the reader to the book structure, including the overall topics the abiotic frame, the organisms, biotics, food web interactions and biodiversity and environmental threats. In addition to laying out the structure, this chapter brings up some overarching concepts such as the niche, generalists versus specialists and factors determining the distribution of organisms in natural ecosystems.

Pelagic food web interactions in Lake Cocibolca, Nicaragua

2000 ◽  
Vol 27 (4) ◽  
pp. 1740-1746 ◽  
Author(s):  
Ingemar Ahlgren ◽  
Rolf Erikson ◽  
Luis Moreno ◽  
Lorena Pacheco ◽  
Salvador Montenegro-Guillén ◽  
...  
Keyword(s):  
Food Web ◽  
Food Web Interactions ◽  
Pelagic Food Web

Importance of benthic-pelagic coupling in food-web interactions of Kakinada Bay, India

2021 ◽  
Vol 61 ◽  
pp. 101208
Author(s):  
Swagata Sinha ◽  
Arnab Banerjee ◽  
Nabyendu Rakshit ◽  
Akkur V. Raman ◽  
Punyasloke Bhadury ◽  
...  
Keyword(s):  
Food Web ◽  
Food Web Interactions ◽  
Benthic Pelagic Coupling

scholarly journals Predator identity and the nature and strength of food web interactions

2010 ◽  
Vol 79 (6) ◽  
pp. 1164-1171 ◽  
Author(s):  
Lee M. Henry ◽  
Jordan A. Bannerman ◽  
David R. Gillespie ◽  
Bernard D. Roitberg
Keyword(s):  
Food Web ◽  
Food Web Interactions ◽  
Predator Identity

Functional diversity alters the effects of a pulse perturbation on the dynamics of tritrophic food webs

2021 ◽  
Author(s):  
Ruben Ceulemans ◽  
Laurie Anne Myriam Wojcik ◽  
Ursula Gaedke
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Functional Diversity ◽  
Feedback Loop ◽  
Environmental Changes ◽  
Biodiversity Loss ◽  
Trophic Levels ◽  
Nutrient Pulse ◽  
Trade Offs ◽  
Food Web Model

Biodiversity decline causes a loss of functional diversity, which threatens ecosystems through a dangerous feedback loop: this loss may hamper ecosystems' ability to buffer environmental changes, leading to further biodiversity losses. In this context, the increasing frequency of climate and human-induced excessive loading of nutrients causes major problems in aquatic systems. Previous studies investigating how functional diversity influences the response of food webs to disturbances have mainly considered systems with at most two functionally diverse trophic levels. Here, we investigate the effects of a nutrient pulse on the resistance, resilience and elasticity of a tritrophic---and thus more realistic---plankton food web model depending on its functional diversity. We compare a non-adaptive food chain with no diversity to a highly diverse food web with three adaptive trophic levels. The species fitness differences are balanced through trade-offs between defense/growth rate for prey and selectivity/half-saturation constant for predators. We showed that the resistance, resilience and elasticity of tritrophic food webs decreased with larger perturbation sizes and depended on the state of the system when the perturbation occured. Importantly, we found that a more diverse food web was generally more resistant, resilient, and elastic. Particularly, functional diversity dampened the probability of a regime shift towards a non-desirable alternative state. In addition, despite the complex influence of the shape and type of the dynamical attractors, the basal-intermediate interaction determined the robustness against a nutrient pulse. This relationship was strongly influenced by the diversity present and the third trophic level. Overall, using a food web model of realistic complexity, this study confirms the destructive potential of the positive feedback loop between biodiversity loss and robustness, by uncovering mechanisms leading to a decrease in resistance, resilience and elasticity as functional diversity declines.

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