Maternal effects are no match for stressful conditions: a test of the maternal match hypothesis in a common zooplankter

Anticipatory parental effects modulate population responses to environmental conditions and so are predicted to play a large role in the responses of organisms to global change. In response to one such aspect of global change, the eutrophication of freshwaters and associated blooms of the toxin‐producing cyanobacteria species Microcystis aeruginosa, the rotifer Brachionus calyciflorus produces larger offspring. We hypothesized that rotifers, with their short generational times, exposed to highly predictable cyanobacteria bloom conditions, may adaptively increase offspring investment and offspring fitness (i.e. the maternal match hypothesis). We explicitly tested the consequences of this differential investment by rearing offspring produced by rotifers reared under Microcystis and the nontoxigenic green alga Chlamydomonas, in a full factorial design, where offspring were raised under the maternal diet or the opposite food source. We measured age‐specific fecundity, survival and population growth rates under these conditions and found that maternal exposure to Microcystis decreased offspring survival and fecundity, regardless of offspring diet. Population growth rates, tested using aster models, differed significantly among maternal and neonate diets, but there was no significant interaction between the two factors. Our evidence thus leads us to reject the maternal match hypothesis in this case of rotifer–toxigenic algal bloom interactions and provides further support that toxigenic algal blooms may have extensive effects on grazer populations in ways that are not evaluated using traditional, single‐generation experimental methods.Funding was provided by the Oklahoma Department of Wildlife Conservation (through the Sport Fish Restoration Program, Grant F‐61‐R to K.D.H), the University of Oklahoma Department of Biology and the University of Oklahoma Biological Station (through a Graduate Research Fellowship to J.E.B).Ye

Increased Habitat Connectivity Homogenizes Freshwater Communities: Historical and Landscape Perspectives

Increases in habitat connectivity can have consequences for taxonomic, functional, and genetic diversity of communities. Previously isolated aquatic habitats were connected with canals and pipelines in the largest water development project in the US history, the Columbia Basin Project (CBP; eastern Washington, USA), which also altered environmental conditions; however, the ecological consequences are largely unknown. Using a historical dataset, we examined long-term patterns in zooplankton communities, water chemistry and clarity, testing the hypothesis that increased connectivity will result in taxonomic homogenization. Further, we tested contemporary drivers of communities using a comprehensive set of environmental and landscape variables. Waterbodies were sampled for zooplankton community composition as well as physical and chemical variables inside and outside the CBP using methods consistent with historical studies. We found significant declines in salinity inside the CBP, whereas changes in water clarity were prevalent across all waterbodies. Increased connectivity via canals homogenized zooplankton communities over time, as well as increasing regional richness. Other long-term changes in zooplankton communities may be related to climate change, invasive species, and land-use changes. Synthesis and applications. Though canals may offer species spatial refugia, homogenization may decrease resilience to environmental stressors. These new hybrid aquatic landscapes, or hydroscapes, should be considered carefully in future water development, including specific plans for monitoring of species and environmental conditions, as well as mitigation of undesirable conditions and/or non-native species

Impacts of Hurricane Irene and Tropical Storm Lee on the ecology of the Hudson River Estuary

Between 27 August 2011 and 15 September 2011, the Hudson River Estuary was subjected to two named weather events: Hurricane Irene and Tropical Storm Lee. An ongoing sampling programme enabled the collection of pre-storm, post-storm and prior year data of physical, chemical and biological parameters at eight locations within or adjacent to the Estuary, including the upper Hudson River and the Mohawk River. Samples were analysed to determine the degree of impact by Hurricane Irene and Tropical Storm Lee. Suspended solids and water clarity showed significant changes, particularly at the confluence of the Mohawk River. Total phosphorus, pH and conductivity were all significantly different following the storms, but no identifiable change to total nitrogen occurred. Physical parameters associated with the Mohawk River were different pre- and post-storm, but most chemical parameters remained unchanged. Sample locations within the Estuary showed changes to both physical and chemical parameters. Estuary-wide, chlorophyll a concentration and zooplankton density biota were significantly reduced. The data indicate that quantified impacts to water quality lasted for up to three months. An assessment of these results leads to the conclusion that anthropogenic influences within and surrounding the Estuary exacerbated the ecological impacts of these storms