Marine Benthic Invertebrates in Mamala Bay, Oahu, Hawaii 1994 (NODC Accession 9900151)

Planktonic larval stages of many benthic marine invertebrates are especially susceptible to environmental stress, such as the presence of pollution. Recruitment of these larvae onto the seafloor frequently controls benthic community structure. We thus evaluated larval availability and recruitment of macrobenthos over a period of 14 months at 12 stations within Mamala Bay, to assess the ecosystem impacts of major point and non-point sources of pollution. The major point source of pollution in the Bay, the Sand Island outfall, had no detectable negative impact on larval recruitment, even though the sewage plume frequently bathed our stations nearest the outfall. In contrast, larval availability and recruitment were significantly reduced at two study sites located 1 km west of the Pearl Harbor Channel (1 and 3 km offshore respectively). These two sites are likely bathed by a larval- depleted water mass whose source is not presently known. Possible sources include: 1) Pearl Harbor, whose outflow may be larval-depleted due to larval mortality caused by non-point source pollution, or the settlement of larvae inside Pearl Harbor before they are advected offshore (recruitment shadow), 2) offshore waters, or 3) coastal waters west of Pearl Harbor. It is difficult to determine the source(s) of waters bathing our offshore Pearl Harbor study sites because circulation patterns in the area are complicated by the convergence of semi-diurnal tidal flows located offshore of the area between Keehi Lagoon and the Honouliuli outfall (MB-6). The scale of hydrographic observations conducted as part of MB-6 were spatially too coarse to determine the location of the convergence therefore making it impossible to determine the source of water that most frequently bathes our western offshore Pearl Harbor study sites. Outflow from Keehi Lagoon produced a distinct, low-clarity water mass which appeared to enhance larval availability and recruitment of some taxa (especially balanomorph barnacles). Coral recruitment rates were extremely low across the bay (6 x 10-5 cm-2). Low coral recruitment rates are most likely due to inadequate larval supply since percent cover of live adult coral (coral larval source) is less than 5% throughout most of the bay. Coral recruitment rates observed in earlier studies in Maunalua Bay (located east of Diamond Head), which has similar live coral cover and few significant inputs of pollution, are also extremely low. This suggests that pollution inputs to Mamala Bay are not responsible for the observed low coral recruitment rates.

Tags: benthic, benthic survey, biological survey, biology, biosphere, central pacific ocean, coastal studies, corals, coris_metadata, country/territory, earth science, hawaii, hawaiian islands, honolulu, invertebrate larval availability, invertebrate larval recruitment rates, larvae, larval dispersal, larval settlement, mamala bay, marine benthic invertebrate type and abundance, marine biology, marine invertebrates, mhi, numeric data sets, oahu, oahu (21n157w0003), oahu island, ocean basin, oceans, pacific ocean, reproduction, sexual reproduction, united states of america, zoology
Organization: National Oceanic and Atmospheric Administration, Department of Commerce