Invertebrate communities of groundwater-dependent refugia with varying hydrology and riparian cover during a supraseasonal drought

Abstract

Extreme disturbances eliminate aquatic biota and alter community structure and function. During a supraseasonal drought in north-central Texas in the summer and fall 2006, macroinvertebrate communities from persistent groundwater-dependent macrohabitats of varying hydrology and riparian shading were investigated to study their role as invertebrate refugia, and to characterize the taxonomic and functional community structure of benthic assemblages. Ash Creek was the only stream with surface flow within a 35-km radius during the drought. Two perennial and three intermittent stream sites were studied that included perennial riffles, a perennial pool, shaded disconnected pools, and disconnected pools in full sun. Riffles had significantly higher taxa richness, EPT (Ephemeroptera, Plecoptera, and Trichoptera) richness, proportion of lotic taxa, and diversity than other macrohabitats. Macrohabitats were refugia for 106 benthic macroinvertebrate taxa, and perennially flowing habitats contained 19 taxa (17.9% of total taxa) not collected in disconnected pools. Larvae and pupae of caddisflies Marilia spp., Oecetis spp., Helicopsyche spp., and riffle beetle Microcylloepus spp. larvae and adults demonstrated resistance to drought by their presence in shaded disconnected pools without surface flow for over a month. Gathering-collectors were the most dominant and taxonomically diverse functional feeding group (FFG) in all macrohabitats. Scrapers ranked second in dominance in riffles, followed by predators; however, predators were the second most dominant FFG in all pool habitats. Continued overabstraction of groundwater in the region could lead to loss of perennial riffles and pools and extirpation of lotic taxa, such as Lutrochus spp., Mayatrichia spp., and Marilia spp., and dramatically alter community structure and function.Keywords: drought refugia; aquatic insect community; headwater stream; groundwater-dependent ecosystem; perennial stream IntroductionThe north-central region of Texas, with rainfall totaling less than 882 mm annually, is a semiarid ecosystem (NOAA 2012a). The region has many small streams and springs that are important to the maintenance of aquatic diversity and community structure (Brune 2002). The aquatic invertebrates found in these streams are important links between primary producers and secondary consumers in these systems. Because these streams are dependent on groundwater and springs to maintain flow, reductions to these water sources caused by droughts have been recognized as important forces shaping invertebrate assemblages in streams (Grimm and Fisher 1989;Dudley et al. 1990;Boulton and Lake 1992a;Stanley and Fisher 1992). Lake (2003) distinguished between two types of droughts: seasonal and supraseasonal. Organisms in streams subjected to predictable seasonal droughts *Corresponding author. Email: rburk1@atu.edu 252 R. A. Burk and J.H. Kennedy are more likely to have evolved adaptations to survive reduced or lack of flow. However, supraseasonal droughts cannot be foreseen and build gradu...

Shifts in aquatic macroinvertebrate community structure in response to perenniality, southern Cape, South Africa

“…The non-perennial stream shifted towards aquatic macroinverterbate communities consisting more of generalist, opportunistic species driven by flow conditions. Macroinvertebrate response to changing environmental conditions thus becomes predictable, where reduced or no flows causes taxa less resilient to change to perish and the resumption of flows after no-flow periods allows macroinvertebrate communities to slowly re-establish in the biotopes (Burt & Kennedy 2013).…”

Climate change vulnerability assessment of aquatic and terrestrial ecosystems in the U.S. Forest Service Rocky Mountain Region

“…Functioning riparian areas enhance aquatic species resilience as riparian plants can stabilize banks and provide organic matter to aquatic species . Springs, seeps, and groundwater connections in some Great Plains streams can, on a local level, mitigate drier conditions (Burk and Kennedy 2013;Dodds et al 2004).…”

“…Although crayfish and many other benthic macroinvertebrates survive drought and flooding by adapting their life history behaviors and movement, Fritz and Dodds (2004) reported that recolonization from unaffected areas was a primary means of recovery in northeastern Kansas. Burk and Kennedy (2013) noted the importance of groundwater-dependent refugia for macroinvertebrate communities in the recent drought in Texas. Recovery of communities under future warming and drought will depend on the ability of species to adapt, and also the availability of habitat along the streams that species may recolonize after drying periods.…”

“…For intermittent streams on the Konza Prairie in Kansas, Costigan et al (2015) concluded that local water-table fluctuations and soil moisture conditions control hydrological responses more than do local weather patterns. Burk and Kennedy (2013) noted the importance of groundwater-dependent places of refuge for aquatic species. Using 12 different future climate projections, Perkin et al (2010) reported that climate change effects on stream fragments will vary regionally; the northern Great Plains may see increases in streamflow whereas Nebraska and Kansas in the southern Great Plains may see declines.…”

“…Groundwater connections, springs, and seeps can be important sources of moisture during drier conditions. Spring-fed streams or groundwater, along with riparian vegetation, can help maintain suitable aquatic temperatures as air temperatures increase and warm these habitats under climate change (Burk and Kennedy 2013;Falke et al 2012). Some Great Plains streams dominated by cottonwoods and willows can support beaver populations (Robel et al 1993).…”