Trait-based approaches to zooplankton communities

Zooplankton are major primary consumers and predators in most aquatic ecosystems. They exhibit tremendous diversity of traits, ecological strategies and, consequently, impacts on other trophic levels and the cycling of materials and energy. An adequate representation of this diversity in community and ecosystem models is necessary to generate realistic predictions on the functioning of aquatic ecosystems but remains extremely challenging. We propose that the use of trait-based approaches is a promising way to reduce complexity while retaining realism in developing novel descriptions of zooplankton in ecosystem models. Characterizing zooplankton traits and trade-offs will also be helpful in understanding the selection pressures and diversity patterns that emerge in different ecosystems along major environmental gradients. Zooplankton traits can be characterized according to their function and type. Some traits, such as body size and motility, transcend several functions and are major determinants of zooplankton ecological strategies. Future developments of trait-based approaches to zooplankton should assemble a comprehensive matrix of key traits for diverse groups and explore it for general patterns; develop novel predictive models that explicitly incorporate traits and associated trade-offs; and utilize these traits to explain and predict zooplankton community structure and dynamics under different environmental conditions, including global change scenarios. © 2013 The Author

Antipredator behaviours of a spider mite in response to cues of dangerous and harmless predators

Prey are known to invest in costly antipredator behaviour when perceiving cues of dangerous, but not of relatively harmless predators. Whereas most studies investigate one type of antipredator behaviour, we studied several types (changes in oviposition, in escape and avoidance behaviour) in the spider mite Tetranychus evansi in response to cues from two predatory mites. The predator Phytoseiulus longipes is considered a dangerous predator for T. evansi, whereas Phytoseiulus macropilis has a low predation rate on this prey, thus is a much less dangerous predator. Spider mite females oviposited less on leaf disc halves with predator cues than on clean disc halves, independent of the predator species. On entire leaf discs, they laid fewer eggs in the presence of cues of the dangerous predator than on clean discs, but not in the presence of cues of the harmless predator. Furthermore, the spider mites escaped more often from discs with cues of the dangerous predator than from discs without predator cues, but they did not escape more from discs with cues of the harmless predator. The spider mites did not avoid plants with conspecifics and predators. We conclude that the spider mites displayed several different antipredator responses to the same predator species, and that some of these antipredator responses were stronger with cues of dangerous predators than with cues of harmless predators

Phylogeography of Neomysis americana (Crustacea, Mysida), focusing on the St. Lawrence system

AbstractSpecies characterized by low dispersal capacities, such as mysids, usually show evidence of genetic differentiation. Many mysids are broadly distributed and often show eurythermal and euryhaline traits. This study aimed to describe intraspecific genetic structure and the phylogeography of Neomysis americana, a key species of estuarine food webs in northwest Atlantic, using the mitochondrial cytochrome c oxidase subunit I gene. We sampled 26 populations across the St. Lawrence system (SLS) and two along the east coast of North America [Penobscot and Chesapeake Bay (CB)]. Sequencing of 420 individuals revealed three divergent (&amp;gt;3%) lineages (LA, LB, LC) across the sampling area suggesting that N. americana represents a cryptic species complex. The distribution of the lineages was geographically structured. LC occurred in the CB only, whereas LA and LB co-occurred along the SLS and Penobscot Bay. This suggests secondary contact after the last glacial maximum. In the SLS the lineage LA dominated the estuarine transition zone and the Gulf of St. Lawrence, whereas the lineage LB was prevalent in the lower St. Lawrence Estuary, potentially due to different eco-physiological preferences. These results might help to define reasonable entities for research and management.</jats:p

Juvenile Alewife (Alosa pseudoharengus) Movement and Residency in a Northern Temperate Estuary

Information on juvenile alewife use of estuaries is limited on the east coast of North America. In this study, we collected juvenile alewife from the Penobscot River estuary, Maine, and measured stable isotope values from their muscle and liver tissues, which have a low and high turnover rate (respectively). These values were compared to the stable isotope values of preferred prey taxa collected from three distinctly different isotopic habitats within the Penobscot River watershed to estimate the amount of time fish had spent in the estuary. Fish were collected in spring, summer, and autumn in 2013 and 2014 at seven fixed collection sites in the estuary, from four freshwater lakes, and from five bay locations. Based on the δ13C values of muscle and liver tissue, estuarine caught juvenile alewife were assigned to one of the following distinctly different isotopic habitat groups: freshwater transient (recently from freshwater), bay transient (recently from the bay), or estuarine occupant (spent extended time in the estuary). Stable isotope ratios of nitrogen (for all samples) and sulfur (in muscle tissues of a subset of 17 samples) were analyzed to confirm habitat group designations. Bay transients had 37% and 15% higher sulfur and nitrogen isotope ratio values than estuarine occupants and five times more sulfur and almost two times more nitrogen isotope ratio values than freshwater transients. Of 88 juvenile alewife analyzed for carbon isotopes, 32% were identified as estuarine occupants that had spent extended time periods in the estuary, whereas 68% of juvenile alewife had recently moved from bay or freshwater habitats. Mean number of days that juvenile alewife spent in the estuary was highest in spring and declined over time, with more movement occurring in autumn. This result suggests that movement of juvenile alewife between bay and estuary occurs frequently from May to October. Juvenile alewife may use estuarine and nearshore habitats for extended time periods, and migration between estuarine and bay habitats may not follow typical life history strategies

Data from: Intoxicated copepods: ingesting toxic phytoplankton leads to risky behaviour

Understanding interactions between harmful algal bloom (HAB) species and their grazers is essential for determining mechanisms of bloom proliferation and termination. We exposed the common calanoid copepod, Temora longicornis to the harmful algal bloom species Alexandrium fundyense and examined effects on copepod survival, ingestion, egg production and swimming behaviour. A. fundyense was readily ingested by T. longicornis and significantly altered copepod swimming behaviour without affecting copepod survival or fitness. A. fundyense caused T. longicornis to increase their swimming speed and the straightness of their path long after the copepods had been removed from the A. fundyense treatment. Models suggest that these changes could lead to a 25-56% increase in encounter frequency between copepods and their predators. This work highlights the need to determine how ingesting HAB species alters grazer behaviour as this can have significant impacts on the fate of HAB toxins in marine systems