Reproductive biology and biochemical composition of the brooding echinoid <Emphasis Type="Italic">Amphipneustes lorioli</Emphasis> on the Antarctic continental shelf

The bathyal West Antarctic Peninsula (WAP) shelf experiences intense seasonal variability in primary production, with summer phytoplankton blooms yielding intense pulse of phytodetritus to shelf sediments. Echinoderms form a conspicuous proportion of the deposit-feeding megabenthos on the shelf and of these Amphipneustes lorioli was the most abundant irregular echinoid. To explore the reproductive response of A. lorioli to this seasonal production cycle, A. Lorioli was sampled at one location on the WAP shelf during four separate cruises between March 2000 and March 2001. Reproductive patterns were determined by histological analyses of gonad tissue, and elemental (CHN) analyses were used to estimate the nutritional and energetic status of the body tissues. Histological analysis of the brooding echinoid A. lorioli suggested a quasi-continuous gametogenic pattern in both the ovaries and the testes. Biochemical analysis of the gonads and the gut tissues were consistent with a continuous gametogenic cycle, showing no significant changes in the biochemical composition of the tissues among seasons. Size-frequency distributions of the embryo and juvenile echinoids within the adults’ brood pouches revealed a synchronous recruitment of embryos and juveniles in specific cohorts between different adult specimens. Whilst this occurrence of different cohorts of the developing brood may be an adaptation to limited brood space, there may also be an external factor influencing the synchrony between adult individuals. Nonetheless, a continuous gametogenic cycle and the lack of seasonal variation in the biochemical composition of gonad and gut tissues suggest that this deposit-feeding irregular urchin is exploiting a persistent sediment food bank in WAP shelf sediments throughout much of the year.     

Antarctic shallow-water mega-epibenthos: shaped by circumpolar dispersion or local conditions?

The mega-epibenthos of two different geographic areas, the Antarctic Peninsula and the high Antarctic (eastern Weddell Sea), were investigated using underwater video. The distribution of the marine fauna at shallow depths between 55 and 160 m in these two areas was investigated to determine whether there are any zoogeographic differences at the community level. A total of 237 taxa represented by 85,538 individuals was identified. Multivariate analyses revealed significant faunal differences between northern Marguerite Bay (western Antarctic Peninsula) and the stations from the Weddell Sea, Atka Bay and Four-Seasons Bank. Echinoderms, especially ophiuroids, dominated Marguerite Bay, bryozoans and ascidians were abundant at Atka Bay, and hydroids and gorgonians were well represented at Four-Seasons Bank. These clear differences can mainly be explained by the influence of local environmental conditions that are probably the primary feature responsible in shaping the Antarctic shallow-water epifauna and not an intensive exchange with larger depths or a limited dispersion due to scarce and isolated shallow areas. In addition, modes of reproduction and characteristics of the early life history (e.g. brooding, viviparity or budding) of key taxa may also shape patterns of species distribution in shallow benthic Antarctic communities.Communicated by O. Kinne, Oldendorf/Luhe     

Co-ordinated rhythms of digestion,absorption and excretion in Mytilus edulis (Bivalvia: Mollusca)

Sequential alternation of extracellular digestion in the stomach and intracellular digestion in the diverticula appears widespread among bivalves. The present study documents some physiological consequences of such processes in Mytilus edulis L. collected during 1981 from Whitsand Bay, Cornwall, England. Pronounced temporal fluctuations in faecal deposition are described that relate, in terms of amplitude and period, to both sinusoidal rhythmicity established for ammonia excretion and changes in the morphology of digestive tubules. Although at least partially synchronised among replicate groups of mussels, these cycles bore no consistent relationship with exogenous influences. Hourly fluctuation in the net absorption efficiency for nitrogen, as evidenced by the mean percentage ±2 SE, measured over 24 h sampling periods, was considerable (16.0±53.7, 49.3±10.9 and 52.8±6.6 for mussels acclimated in March, June and October, respectively). This variation in absorption derived from an inverse relationship between the percentage nitrogen within faeces and the rate of faecal egestion. Accordingly, peaks of faecal deposition presumably represented the pulsed remnants of intracellular digestion. Co-ordinated rhythms of digestion, absorption and excretion were thus evident in M. edulis. These processes displayed seasonally dependent periodicities of approximately 8, 3 and 4 h in March, June and October, respectively. It was concluded that, at least for M. edulis, this previously unquantified rhythmicity of physiological processes warrants careful consideration during assays commonly undertaken in the complication of nutrient and energy budgets.     

Increases in Nitrate Concentrations in the River Frome (Dorset) Catchment Related to Changes in Land Use, Fertiliser Applications and Sewage Input

Nitrate concentrations and nitrate loads throughout the River Frome catchment (Dorset) are compared for the periods 1970-71 and 1984-86. Nitrate concentrations and loads have increased at every site, the increase in mean nitrate concentrations varying from 31% to 123%. These increases in nitrate concentrations are related to changes in land use and fertiliser applications and also to an increase in sewage effluent entering the river.     

Potentially harmful elements in house dust from Estarreja,Portugal: characterization and genotoxicity of the bioaccessible fraction

Due to their behavioral characteristics, young children are vulnerable to the ingestion of indoor dust, often contaminated with chemicals that are potentially harmful. Exposure to potentially harmful elements (PHEs) is currently exacerbated by their widespread use in several industrial, agricultural, domestic and technological applications. PHEs cause adverse health effects on immune and nervous systems and can lead to cancer development via genotoxic mechanisms. The present study is an integrated approach that aims at assessing the genotoxicity of bioaccessible PHEs following ingestion of contaminated house dust. A multidisciplinary methodology associating chemical characterization of five house dust samples, extraction of the bioaccessible PHEs in gastric extracts by the unified BARGE method, determination of the bioaccessible fraction and in vitro genotoxicity of gastric extracts in adenocarcinoma gastric human (AGS) cells was developed. The five gastric extracts induced dose-dependent genotoxicity in AGS cells. Copper (bioaccessible concentration up to 111 mg/kg) was probably the prevalent PHE inducing primary DNA damage (up to 5.1-fold increase in tail DNA at 0.53 g/l of gastric extract). Lead (bioaccessible concentration up to 245 mg/kg) was the most prevalent PHE inducing chromosome-damaging effects (r = 0.55; p < 0.001 for micronucleated cells induction). The association of principal component analysis and Spearman’s correlations was decisive to understand the chromosome-damaging properties of the bioaccessible PHEs in AGS cells. This methodology could be used on a larger-scale study to provide useful information for science-based decision-making in regulatory policies, and a better estimation of human exposure and associated health risks.     

Global rarity of intact coastal regions

Management of the land–sea interface is essential for global conservation and sustainability objectives because coastal regions maintain natural processes that support biodiversity and the livelihood of billions of people. However, assessments of coastal regions have focused strictly on either the terrestrial or marine realm. Consequently, understanding of the overall state of Earth's coastal regions is poor. We integrated the terrestrial human footprint and marine cumulative human impact maps in a global assessment of the anthropogenic pressures affecting coastal regions. Of coastal regions globally, 15.5% had low anthropogenic pressure, mostly in Canada, Russia, and Greenland. Conversely, 47.9% of coastal regions were heavily affected by humanity, and in most countries (84.1%) >50% of their coastal regions were degraded. Nearly half (43.3%) of protected areas across coastal regions were exposed to high human pressures. To meet global sustainability objectives, all nations must undertake greater actions to preserve and restore the coastal regions within their borders.