Ecological insights into the polyp stage of non-native hydrozoans in the San Francisco Estuary

Abstract

The populations of several invasive jellyfish appear to be increasing around the globe. While data on non-native hydromedusae in the San Francisco Estuary have been accumulating in recent years, little is known regarding their polyp phase. The goal of this study was to gather the first field-derived ecological data for polyp stages of Blackfordia virginica, Moerisia sp., and Cordylophora caspia in the estuary. Monthly fouling plates were deployed at five sites during 2007 and 2008. Settlement data indicate a seasonal presence of B. virginica and Moerisia sp., with both distribution and abundance correlated with a combination of water quality and physical parameters. Cordylophora caspia appeared to be present beyond the time period sampled and may be active in the system year-round. The ability of polyps to persist month to month was low, likely due to predation by other non-native species and competition for space.

First record of the non-indigenous jellyfish Blackfordia virginica (Mayer, 1910) in the Baltic Sea

“…virginica is a hydromedusa, characterised by an alternation between benthic and pelagic life forms. Medusa production from benthic polyps has been suggested to occur throughout the entire summer period in northwestern America [20,34]. Locations of polyp settling in Kiel Canal remain to be identified.…”

Invasive Ponto-Caspian hydrozoan Cordylophora caspia (hydrozoa: Cnidaria) in southern Baltic coastal lakes

“…Ecological consequences of invasion of aquatic habitats by C. caspia are less clearly recognized, but they are likely harmful. The species transforms ecosystems by growing dense colonies on a variety of immersed surfaces, including rocks, floating and emergent vegetation, and even the dorsal surface of live fish (Wintzer et al, 2011). Such habitat modifiers directly or indirectly influence the availability of resources to other species and can have large effect on associated biota (Duedero et al, 2011).…”

“…In Poland it occurs in the River Odra Estuary (Gruszka, 1999) but other than that it has not yet been observed in fresh water environments. The species clearly profits from eutrophication and global shifts in thermal and salinity regimes (Wintzer et al, 2011;Meek et al, 2012). Invasion of C. caspia has serious economic consequences.…”

Food Webs of the Delta, Suisun Bay, and Suisun Marsh: An Update on Current Understanding and Possibilities for Management

“…The introductions likely resulted from ballast water release (Rees and Gershwin 2000). Medusae are seasonally abundant in the harbors and sloughs of the estuary (Rees and Kitting 2002;Schroeter 2008;Wintzer et al 2011aWintzer et al , 2011c but are not sampled well by existing sampling programs. They consume copepods, especially nauplii (Wintzer et al 2011b, and in Suisun Marsh their diets overlap with those of Threadfin Shad and Delta Smelt (Wintzer et al 2011c The changes in lower trophic levels were followed by shifts in diets, distributions, and abundance of many fish species.…”

“…Medusae are seasonally abundant in the harbors and sloughs of the estuary (Rees and Kitting 2002;Schroeter 2008;Wintzer et al 2011aWintzer et al , 2011c but are not sampled well by existing sampling programs. They consume copepods, especially nauplii (Wintzer et al 2011b, and in Suisun Marsh their diets overlap with those of Threadfin Shad and Delta Smelt (Wintzer et al 2011c The changes in lower trophic levels were followed by shifts in diets, distributions, and abundance of many fish species. For example, during 1998-1999, the stomachs of Striped Bass, Splittail Pogonichthys macrolepidotus, and three other species in Suisun Marsh were less full than those of fishes caught during 1979-1983(Feyrer et al 2003.…”