The reliability of analytical data for tributyltin (TBT) in sea water and its implications on water quality criteria

To investigate the reliability of analytical data for tributyltin (TBT) in sea water, split water samples were distributed to ten laboratories in six countries. The sub-surface samples comprised: (i) an offshore (0·5 km) water sample, (ii) the same sample but spiked with an undisclosed quantity of TBT standard compound (175 ng TBT⁺ liter⁻¹), and (iii) a sample taken from a yacht marina. The seven acceptable data sets were in good agreement for the spiked sample (178 ± 26 ng TBT⁺ liter⁻¹) but showed a greater variation in concentrations reported for the yacht marina sample (366 ± 93 ng TBT⁺ liter⁻¹). Atomic absorption and gas chromatographic-flame photometric detection techniques produced results of similar accuracy and precision. Samples acidified with 1 ml of 10% (v/v) acetic acid appeared stable for more than 2 weeks when stored refrigerated and in darkness. Analyses of the offshore seawater sample revealed TBT contamination (9 ± 7 ng TBT⁺ liter⁻¹) indicating dispersion of the compound to the shelf waters off Monaco. The spread in values reported by the laboratories demonstrates inherent difficulties in obtaining good precision below approximately 20 ng TBT⁺ liter⁻¹. This observation is discussed with respect to the setting and enforcing of water quality standards.     

Seasonal methyltin and (3-dimethylsulphonio)propionate concentrations in leaf tissue of Spartina alterniflora of the Great Bay estuary (NH)

Concentrations of total recoverable inorganic tin (TRISn), monomethyltin (MeSn³⁺), dimethyltin (Me₂Sn²⁺), trimethyltin (Me₃Sn⁺) and (3-dimethylsulphonio)propionate (DMSP) were determined in leaves of Spartina alterniflora from three sites in the Great Bay estuary (NH) from 8 May to 15 September 1989. Total methyltin concentration increased from 8·9 ng g⁻¹ (fresh weight) on 8 May to 472 ng g⁻¹ on 23 May, decreased to 52 ng g⁻¹ on 7 June and 16ng g⁻¹ on 20 June, and remained low until the last sample on 18 September. Statistical calculations showed that methyltin concentrations varied significantly with sampling week, but not with site. DMSP concentrations showed very different behaviour. During the same sampling period DMSP concentrations varied only from 7·5 to 26 μmol g⁻¹ (fresh weight). DMSP concentrations varied significantly for site, but not sampling week.     

Sedimentary development of the Louisiana continental shelf related to sea level cycles: Part II—seismic response

Cyclic sequences occur worldwide in nearly every stratigraphic sequence; they are particularly well-developed in fluvial and deltaic sediments that have been influenced by high-frequency eustatic sea-level fluctuations. The large data base for this study (including 471 deep foundation borings, thousands of line kilometers of high-resolution seismic, and sedimentological and dating analyses) represents the most complete information on high-resolution chronostratigraphy and lithostratigraphy that is available on any modern continental shelf/upper slope. These data are used to document sedimentological characteristics and high-resolution seismic responses during three complete sea-level cycles over the entire continental shelf/upper slope of offshore Louisiana. Examination of high-resolution seismic records indicates that well-defined, high-amplitude, laterally continuous reflectors correlate with rising and high stand condensed sedimentary sequences and that the deposits laid down during falling and low-stand periods (expanded sections) are characterized by a wide range of acoustic responses. Discontinuous reflectors with high-amplitude variability, continuous parallel reflectors, and chaotic and amorphous zones are common acoustic responses. The association between a particular lithofacies and a specific acoustic response on 3.5-kHz records was found to be very poor.     

Mussel Periostracum from Deep-Sea Redox Communities as a Microbial Habitat: 3. Secondary Inhabitants

Abstract. Vacated microborings in periostracum of live mussels of the Florida Escarpment redox community (depth of 3266 m) become a habitat for a prolific secondary microbiota consisting of a variety of prokaryotic and a few eukaryotic organisms. Periostracum surface is also colonized by diverse microorganisms, dominated by presumed chemolithotrophic bacteria with stacks of intracellular lamellae. Unlike sheltered microflora within borings, the surface community is heavily grazed upon by numerous archaeogastropods and ciliates.     

Age and growth of Cape stumpnose Rhabdosargus holubi (Pisces: Sparidae) in the Eastern Cape,South Africa

Rhabdosargus holubi is a small (maximum weight=2.4?kg) yet important fishery species in the estuaries of the south-east coast of South Africa. Little is known of its biology and specifically its growth rate, which is essential for sustainable management of the fishery. We examined and counted the opaque zones in the sectioned otoliths of 134 R. holubi to determine its age and growth parameters. The otoliths from two recaptured fish marked with oxytetracycline confirmed that one opaque zone was deposited annually. The species reached a maximum age of 18 years and growth was adequately described by a von Bertalanffy growth function of the form: L_t = 358.1 (1 – e^{?0.24(t+0.77)}) mm fork length. There were no significant differences between any of the male and female growth parameters (likelihood ratio test: p = 0.3). The growth was slow (omega index: ω = 86.56); however, despite this, the unique life history of R. holubi may provide a degree of resilience to heavy fishing pressure in estuaries.     

Ghost fishing in European waters: Impacts and management responses

In this paper we review levels of net loss, what happens to the gear once it has been lost, and the resulting levels of ‘ghost catches’ made in passive net fisheries in the EU. We also consider ghost catches resulting from lost gear in other types of fisheries, and the extent to which the value of ghost catches has been quantified. We consider why fishing gear is lost, and profile common management responses. We present a cost benefit model to assess the relative cost effectiveness of different management measures, and suggest that gear retrieval programmes may provide less value for money than other management responses.     

Symbiosis between the holothurian Scotoplanes sp. A and the lithodid crab Neolithodes diomedeae on a featureless bathyal sediment plain

Vulnerability to predation may be high for many megafaunal taxa in deep‐sea sedimentary habitats where physical heterogeneity is low. During ROV observations in a bathyal sediment plain off Central California, juveniles of the lithodid crab Neolithodes diomedeae were frequently observed on or under the holothurian (sea cucumber) Scotoplanes sp. A, and are hypothesized to benefit from this association as a nursery or refugium from predation. Ninety‐six percent (n = 574 of 599) of the juvenile N. diomedeae observed (density varied from 0.02–0.75/m² among sites and seasons) in the study area were associated with Scotoplanes sp. A. Of the 2596 Scotoplanes sp. A observed (density varied from 0.48 to 25.90/m²), 22% were attended by at least one juvenile crab, and rarely two crabs (n = 4). Solitary N. diomedeae were rarely observed. This decapod–holothurian symbiosis appears to be largely commensal, with juvenile crabs (carapace width = 0.03–0.31 ×  holothurian length) observed on or beneath Scotoplanes sp. A in a habitat with few refugia from epibenthic predators. Other hypotheses may explain or enhance the potential benefits of the association for N. diomedeae, such as elevated food availability due to the activities of Scotoplanes sp. A. The relationship may be mutualistic if there is a benefit for the holothurian, including the removal of epizoic parasites. Ultimately, the nursery or other effects on the population dynamics of N. diomedeae may be minimal in low‐relief, sediment‐dominated habitats, as very few sub‐adult crabs were observed in the study area and were likely consumed upon outgrowing their refugia. While sedimentary habitats may be a sink for N. diomedeae populations, growth of juvenile crabs during their association with Scotoplanes sp. A should increase energy flow to its predator populations. This association has not been reported previously but may be expected in sediment‐dominated habitats where these species overlap.     

Thioploca spp. sheaths as niches for bacterial and protistan assemblages

Sulfide oxidizing bacterial mats are common in regions of the continental shelves characterized by high primary production and the resultant oxygen minimum zone. These mats are made up of several species of Beggiatoa and/or Thioploca, which oxidize sulfide that is generated in the sediment. Thioploca spp. inhabit a large polysaccharide sheath that encompasses bundles of 1–20 filaments (trichomes), each ranging from 3 to 60 μm in diameter. This sheath has been shown to be a critical component of the autecology of Thioploca. Analysis of Thioploca from cold seeps in Monterey Bay using light and transmission electron microscopy identified new and diverse microbial assemblages associated with interstitial spaces between trichomes, inside the sheath. Small diameter, non‐vacuolate, filamentous prokaryotes were numerous. Amoebae, euglenozoa, ciliates and other protists of unknown affiliation were observed in sheaths. Most of the protists possessed food vacuoles and some protists showed ultrastructural evidence of endosymbionts. These observations suggest that Thioploca sheaths may serve as oases on the sea floor, providing nutritional and detoxification services to previously unrecognized microbial partners.     

Meanders in the Antarctic Polar Frontal Zone and their impact on phytoplankton

The Antarctic Polar Front is a complex set of meandering jets, which appear to support enhanced primary productivity. The US Joint Global Ocean Flux Study conducted a series of survey and process studies in part to study the processes regulating primary productivity in this high nutrient, low chlorophyll region. We deployed a set of surface velocity drifters, some of which were equipped with bio-optical sensors, to study the temporal and spatial scales of biological and physical processes in the Antarctic Polar Frontal Zone. There were two primary sets of deployments: November 1997 before the spring bloom and January 1998 after the spring bloom. The November deployment revealed a strong spring bloom that lasted about 10 days. In late spring, when incoming solar radiation began to increase, the vertical motions associated with the meanders strongly affected the accumulation of phytoplankton biomass, primarily through their impact on light availability. Weaker meandering was observed in the January deployment, and chlorophyll values remained relatively constant. As the bloom began to decay, it appears that nutrient availability became more important in regulating phytoplankton photosynthesis. Some of the drifters in the November deployment were deployed in coherent clusters, thus allowing us to calculate vertical velocities associated with the meanders. Estimates of fluorescence/chlorophyll suggest that areas of upwelling and downwelling alternately decrease and increase photosynthetic stress, perhaps as a result of changes in the availability of iron or light during the formation of the bloom.