High reproduction, but low biomass: mortality estimates of the copepod Acartia tonsa in a hyper-eutrophic estuary

Abstract

Production, abundance and mortality of the copepod Acartia tonsa were studied for a period of 9 d in a hyper-eutrophic estuary, Mariager Fjord, Denmark. The estuary is characterised by oxygen-depleted and often sulphidic bottom water, and a relatively sparse mesozooplankton community with low species diversity. During the study, an intense phytoplankton bloom consisting mainly of the diatom Skeletonema costatum developed with chlorophyll a concentrations reaching 46 μg l , and egg hatching success was > 90%, yet the abundance of copepods remained low (1 to 3 nauplii l ). Calculated daily copepod mortality ranged from 18% for nauplii, 16% for Copepodite Stage C1, up to 70% for C2 and C3, then declining for older stages. The vertical distribution of copepodites in relation to the depth range of mussel beds suggests strong predation by suspension-feeding Mytilus edulis at depths of 5 to 10 m. Moreover, anoxia and the presence of sulphide in deep water, which prevented hatching of A. tonsa eggs and decreased the survivorship of older life stages sinking below 20 m depth, further contributed to the low copepod abundance.

In situ detrimental impacts of Prorocentrum donghaiense blooms on zooplankton in the East China Sea

“…Some studies described the detrimental effects of sulfides on copepods. For example, Tiselius et al (2008) reported that rich sulfide levels in deep water decreased the survivorship of A. tonsa. Exposure to sulfide also affected the survival rates of male Cletocamptus confluens (Vopel et al, 1998) and the hatching success of A. tonsa (Nielsen et al, 2006).…”

Hundred years of genetic structure in a sediment revived diatom population

“…Because the deeper part of the inner fjord is anoxic, there is no infauna and therefore no bioturbation. The Mariager Fjord has a sparse mesozooplankton community and periodically intense blooms of S. marinoi (38).…”

Abiotic and biotic controls on the copepod Pseudodiaptomus forbesi in the upper San Francisco Estuary

“…Furthermore, a favorable feeding environment can enable an animal to acclimate to salinity outside its optimum range (Lee et al 2013). Therefore, the distribution of a cope pod species in salinity space likely arises through a combination of salinity tolerance with behaviorally mediated retention mechanisms (Hough & Naylor 1991, Simons et al 2006, Kimmerer et al 2014a) and spatially variable growth and mortality (Barlow 1955, Stalder & Marcus 1997, Tiselius et al 2008) that may offset effects of unfavorable salinity (Lee et al 2013, Hammock et al 2016 or restrict distributions to only part of the tolerated range (Rippingale & Hodgkin 1975).…”