We evaluated copepod taxonomic diversity as a potential biological indicator of ocean conditions in the northeast Pacific Ocean using data collected biweekly between

Upwelling winds off North Carolina set up upwelling fronts. As the wind forcing relaxed following such a coastal upwelling event, we observed the upwelling front move onshore. The low‐density surface water moved shoreward over the upwelled water, forming a convergence zone at the front. This shoreward‐moving front concentrated and transported larvae. Larval sergestid shrimp, spionid polychaete larvae, and the veligers of Odostomia sp. and Bittium sp. were concentrated on the seaward side of the moving convergence. Blue crab megalopae were concentrated at the surface immediately seaward of the front. These data demonstrate that a relaxing upwelling front can transport high concentrations of larvae shoreward over the inner shelf. This may be an important mechanism promoting the shoreward migration of larval invertebrates and fish.

Despite a dramatic increase in the introduction of non-indigenous estuarine zooplankton in recent decades, the trophic implications of such introductions have rarely been quantified. Here we investigate predation rates of Tortanus dextrilobatus, a carnivorous copepod recently introduced to the San Francisco Estuary that achieves peak abundances in excess of 1000 ind. m . The functional response of T. dextrilobatus feeding upon 2 copepod prey types -the non-indigenous cyclopoid Oithona davisae, and the 'native' calanoid Acartia (Acartiura) sp. -was described by a type II functional response (Ivlev function) at 2 experimental temperatures. In 3 of these 4 treatments, 90% I max was achieved within a naturally occurring range of prey densities. Taxon-specific seasonal size variation was identified, and carbon-based consumption values were used to determine temperature-dependent rates of predation on both prey types. These empirically derived consumption rates and temperature dependence values were then applied to broadscale surveys (1997 to 1999) of zooplankton community composition in order to estimate the predatory impact of T. dextrilobatus upon prey populations in the San Francisco Estuary. Predatory impact estimates (% population consumed d -1 ) greater than 1% occurred on a regular basis when T. dextrilobatus was abundant, with maxima exceeding 20, 65, and 25% for O. davisae, Acartia (Acartiiura) sp. and all Copepoda, respectively. These observations support the hypothesis that non-indigenous invertebrate zooplanktivores can play a significant role, at least seasonally or episodically, in the secondary production dynamics of aquatic ecosystems.KEY WORDS: Zooplankton ecology · Feeding · Predation · Copepods · Tortanus dextrilobatus · Non-indigenous · Invasion · San Francisco Estuary Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 277: [167][168][169][170][171][172][173][174][175][176][177][178][179] 2004 A rapid increase in biological invasions of estuarine habitats in recent decades has increased the prospect of potential deleterious effects on community and ecosystem level dynamics (Carlton & Geller 1991, Ruiz et al. 1997, Parker et al. 1999). Yet, a recent literature review by Bollens et al. (2002) revealed a scarcity of studies exploring such impacts in zooplankton communities, despite widespread documentation of invasion occurrence and mechanisms. Determining the impacts of human mediated introductions has been a challenge for natural resource managers and ecologists alike, and while they may represent unfortunate cases of often inadvertent biomanipulation, they provide a unique opportunity for investigating fundamental questions in plankton community ecology and invasion biology. One such question is the degree to which predation pressures may be important in regulating population dynamics of secondary producers.The San Francisco Estuary has been identified as one of the most highly invaded aquatic ecosystems (Cohen & Carlton 1998), and the zoop...

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