Most ships entering the Great Lakes carry cargo and declare “no-ballast-on board” (NOBOB) status. Approximately 250 of these vessels annually load Great Lakes’ ballast water when they offload inbound cargo and then discharge this water (which has now mixed with residual water previously present in the tanks) when they load outbound cargo. This procedure potentially allows nonindigenous species present in ballast residuals to invade the Great Lakes. We collected residual sediment, water, and associated organisms from 38 NOBOB ships entering the Great Lakes. We recorded seven established Great Lakes’ nonindigenous species, including some discovered since ballast water exchange was implemented. Occurrences of species not yet invaded indicate that this vector provides further opportunity for invasion. Collectively, NOBOB vessels appear to constitute a greater risk than ballasted vessels, as they make up a greater proportion of the traffic entering the lakes (~90%), and they do not undergo ballast exchange. Invertebrates in residual water appear to have a greater opportunity for discharge than those in sediments, although most in the water fraction have already invaded this system. Invertebrate numbers in residual freshwater ballast could be dramatically lowered if these vessels flushed with open-ocean water prior to entering the Great Lakes.

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Deep-sea hydrothermal vent communities are supported by local microbial chemolithoautotrophic production. While nutritional symbiotic associations between microbial primary producers and their metazoan hosts are well characterised, food sources used by the diverse and abundant non symbiont-containing vent species remain poorly known. Vent suspension-and deposit-feeders are usually considered as primary consumers directly relying on free-living microbial primary production, but other sources of particulate organic matter (POM) may also be part of their diet. We investigated the origin, composition and nutritional quality of POM at Axial Volcano (NE Pacific) vents, using microscopic observations, stable isotopic and biochemical analyses. A positive correlation between the stable carbon isotopic composition of POM and that of vent fluid dissolved inorganic carbon (DIC) indicates that the bulk of vent particulate organic carbon is derived from the local chemolithoautotrophic fixation of vent DIC. Low estimates of bacterial and total microbial carbon might reflect a rapid turnover of free-living bacterial biomass in the vent ecosystem. The low microbial fraction, together with the presence of abundant debris, point to the existence of a large detrital fraction in the POM pool. This implies that the previously largely overlooked detrital compartment may be a significant part of the diet of consumers, and that organic matter recycling may be a major process in these ecosystems.

Siphonostomatoid copepods are often numerically important at deep-sea hydrothermal vents but their role in vent food webs has been little investigated. We examined food sources of 2 vent copepod species, Stygiopontius quadrispinosus and Benthoxinus spiculifer, and their potential role in the diet of paralvinellid worms, using a combination of complementary techniques: (1) stable carbon and nitrogen isotopes, (2) fatty acid composition and (3) morphological examination of copepod mouth structures using scanning electron microscopy. All 3 techniques revealed distinct differences between the 2 copepod species. Fatty acid composition identified bacteria as the main food source for both copepod species and indicated that S. quadrispinosus may be more specialised than B. spiculifer. Stable carbon and nitrogen isotopes provided further evidence that the 2 species partition food sources but feed at the same trophic level. The fatty acid composition and stable isotopes of both paralvinellid worms showed that they are generalists, with a varied diet. Further, in samples where S. quadrispinosus were highly abundant, both worms had stable carbon and nitrogen isotopic compositions that indicated that they were feeding on copepods. Although neither worm appeared anatomically equipped for seizing live copepod prey, we suggest that dead copepods may be consumed along with other particulate debris by the paralvinellid worms. The contribution of copepod remains to the detrital pool in these mineral substratum habitats remains to be quantified.

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