Combined impacts of warming and salinisation on trophic interactions and mortality of a specialist ephemeral wetland predator

Abstract

Wetlands are of enormous importance for biodiversity globally but are under increasing risk from multiple stressors driven by ongoing anthropogenic environmental change. As the trophic structure and dynamics of ephemeral wetlands are poorly understood, it is difficult to predict how these biodiverse ecosystems will be impacted by global change. In particular, warming and salinisation are projected to have profound impacts on these wetlands in future. The present study examined the combined effects of warming and salinisation on species interaction strengths and mortality rates for two ephemeral wetland species. Using an ephemeral pond specialist copepod, Lovenula raynerae Suárez‐Morales, Wasserman, & Dalu, (2015) as a model predator species, we applied a functional response approach to derive warming and salinisation effects on trophic interactions with a prey species. Furthermore, the effects of a salinisation gradient on mortality rates of adult copepods were quantified. The predatory copepod exhibited type II functional responses towards larval Culex pipiens mosquito prey, owing to high predation rates at low prey densities. Increased temperatures generally resulted in greater predator feeding rates, whilst increased salinities reduced consumption. However, the effects of temperature and salinity interacted: temperature effects on functional responses were suppressed under heightened salinities. Substantial mortality was observed in both male and female adult L. raynerae at salinity levels exceeding 10 parts per thousand. Warming and salinisation substantially altered interaction strengths in ephemeral wetland ecosystems, with implications for ecosystem function and stability. Furthermore, we demonstrated salinisation thresholds for mortality in an ephemeral wetland specialist, showing that salinisation may threaten the persistence of endemic species. The ongoing effects of warming and salinisation may therefore interact to alter trophic dynamics and species composition in ephemeral wetlands. These stressors should be considered synergistically within management practices.

Metal Distribution and Sediment Quality Variation across Sediment Depths of a Subtropical Ramsar Declared Wetland

“…Wetlands have myriad functional roles in socioecological systems; for example, wetlands in river catchments directly and indirectly contribute to biodiversity, drought relief, flood attenuation, provision of fodder, water storage and purification, and soil protection [7,8]. Despite the essential ecosystem services that wetlands provide, recent studies [2,[9][10][11] have emphasized that wetlands are amongst the most threatened systems, as they are often located in highly productive land space where anthropogenic drainage and pollution is driven by demands for agricultural and urban developments.…”

Freshwater salinisation: a research agenda for a saltier world

“…Existing knowledge on toxicological and individual responses of fish, amphibians, and birds [17,86,103] must be applied to assess salinity-triggered changes in their trophic interactions (e.g., changes in predation rates). At community level, top-down effects (e.g., loss of keystone species due to salinisation [104]) and trophic cascades are receiving increasing attention [79,105]. However, a complete understanding of these interactions as well as more trophic or energetic approaches (e.g., energy fluxes across the food web [40,79]) needs further attention.…”

Predator density modifies mosquito regulation in increasingly complex environments

“…In particular, emergent effects associated with changeable densities of antagonists may reduce or enhance the efficacy of natural enemy populations in controlling pest populations . Multiple predator interactions may manifest in three broad forms: (i) additively, where predators interact independently with their prey irrespective of predator density, (ii) antagonistically, where predator–predator interference reduces impact and thus alleviates prey risk, and (iii) synergistically, where multiple predator effects enhance predatory impacts and therefore increase prey risk . In addition, habitat complexity is also known to alter predatory interactions .…”

“…Conversely, Type III FRs can impart refuge to low density prey populations and may thus allow for population persistence . FR quantifications, importantly, also allow for the explicit assessment of context‐dependency effects on interaction strengths . In particular, recent studies have applied FRs to quantify the prey density‐dependences of emergent multiple predator effects, and others have demonstrated the effects of habitat complexity for interaction strength .…”

“…In particular, recent studies have applied FRs to quantify the prey density‐dependences of emergent multiple predator effects, and others have demonstrated the effects of habitat complexity for interaction strength . In addition, studies have examined the interactive complexities of multiple environmental factors on predator–prey dynamics, which often combine non‐linearly …”