Short-term effects of an oil spill on the West coast of the Cape Peninsula, South Africa

In 1994, the sinking of the ‘Apollo Sea’ off the West coast of South Africa led to the deposition of ca. 2 500 tons of heavy fuel oil over 150 km of coastline. The impact of the spill on rocky shore invertebrates, rock-pool fish fauna and rock lobsters was assessed by conducting surveys shortly after the spill, and again two months later. Where possible, results of these surveys were compared with existing data from before the sinking of the Apollo Sea. Among the fish fauna of rock-pools, changes in total density of fishes were largely due to changes in the abundance ofClinus superciliosus and were within the range of natural variation for the species and the community as a whole. Community structure of the rock-pool fish fauna also remained unaffected. At three of four impacted rocky shore sites no changes could be detected in overall benthic community structure, although the winkleNodilittorina africana was affected. At the fourth site, a boulder beach, statistical analysis showed distinct differences in community structure between heavily and lightly contaminated areas, as well as between all areas compared with previously existing data. There were also significant changes in the lightly oiled areas between the first and second surveys after the spill. Oil-fouled lobster were found at one of three sites investigated. Ca. 7 % of the seabed in this particular area was polluted. Antennae and forelegs of almost all lobsters in the vicinity of the oil were fouled. Examination of the gut-contents confirmed that oil inhibits the ability of lobster to feed. Although there was no evidence that mortalities of lobster were caused by the spill, growth rates may be reduced by the decreased feeding rate. Overall, the impact of the spill was strikingly less than might have been predicted from the effects of other oil spills. Nomenclature: Names of fish species follow Smith & Heemstra (1986).     

Environmental risk assessment; a case study of the Colhuw Beach revetment on the Glamorgan Heritage Coast, Wales

A newly constructed coastal revetment at Colhuw Beach in the Glamorgan Heritage Coast, Wales, UK, was analysed using a recently developed environmental risk assessment package (ERA). Conflict with Heritage Coast conservation objectives is apparent and the act of building such a structure is questioned for a location where maintenance ofnatural beauty is an axiom of the coastal management philosophy. The likelyhood of revetment related environmental consequences of significant magnitude was analysed using estimated probability values derived from Bayesian theory. The damaging impact of the structure on the natural environment is out of all proportion to the level of storm protection afforded to the site. Analyses, such as carried out via ERA, would have shown planners, engineers and environmentalists, the inadequacies of such an investment and management strategy. The ERA approach can help to introduce greater clarity and consistency into decision making processes.     

Environmental risk assessment; a case study of the Colhuw Beach revetment on the Glamorgan Heritage Coast, Wales

A newly constructed coastal revetment at Colhuw Beach in the Glamorgan Heritage Coast, Wales, UK, was analysed using a recently developed environmental risk assessment package (ERA). Conflict with Heritage Coast conservation objectives is apparent and the act of building such a structure is questioned for a location where maintenance ofnatural beauty is an axiom of the coastal management philosophy. The likelyhood of revetment related environmental consequences of significant magnitude was analysed using estimated probability values derived from Bavesian theory. The damaging impact of the structure on the natural environment is out of all proportion to the level of storm protection afforded to the site. Analyses, such as carried out via ERA, would have shown planners, engineers and environmentalists, the inadequacies of such an investment and management strategy. The ERA approach can help to introduce greater clarity and consistency into decision making processes.     

Fishery resource management in Chilika lagoon: a study on coastal conservation in the Eastern Coast of India

A significant proportion of the fishing population comprises small-scale fishermen and many studies illustrate that these people are exploited by middlemen in the process of fish marketing combined with money lending. The negative dependency gives rise to poverty and triggers indiscriminate fish catch that threatens fishery resources depletion. This article explores the root causes of failures in resource-led development from the viewpoint of coastal resource conservation. The study presents a case study of Chilika lagoon, India and focuses on the interaction between small-scale fishermen and middlemen. The findings reveal that most of the small-scale fishermen have been exploited by specific middlemen and the underlying causes of the present fish marketing structure stem from (i) indebtedness and (ii) the unstable situation because of perpetual conflicts over fishery resources among the fishers across Chilika lagoon. Based on these observations, this article presents some recommendations on fishery resource conservation from the perspective of a fish marketing structure.

Sea-water seasonal changes at a heavy tourism investment site on the Jordanian northern coast of the Gulf of Aqaba, Red Sea

The Gulf of Aqaba exhibits a strong seasonality due to convective mixing during winter and stratification during summer. The present study provides a detailed appraisal of summer and winter sea-water characteristics at the northern coast of the Gulf of Aqaba, that is witnessing rapid development and increasing changes in its geomorphological characteristics. Sea-water temperature, salinity, nutrients, and chlorophyll a concentrations were measured biweekly at five coastal and four cross-sectional stations during the periods February to April and July to September 2004. Meteorological conditions were continuously recorded at the Marine Science Station. The coastal study sites included four open coastal stations and a marina with one-way exchange with the open water. The effect of convective mixing was clearly apparent on the sea-water characteristics. Natural seasonal characteristics of higher nutrients and chlorophyll a concentrations were recorded during winter at most of the open coastal stations. In the cross-sectional stations, the concentrations of nutrients and chlorophyll a were not different between the surface and the bottom during winter, but the bottom waters had generally higher concentrations during summer. Some deviations from the natural seasonal cycle were recorded at the marina and other coastal stations. Here, higher nutrient and chlorophyll a concentrations were recorded in summer than in winter. These deviations that are most likely due to anthropogenic effects are discussed.     

Sea-water seasonal changes at a heavy tourism investment site on the Jordanian northern coast of the Gulf of Aqaba,Red Sea

The Gulf of Aqaba exhibits a strong seasonality due to convective mixing during winter and stratification during summer. The present study provides a detailed appraisal of summer and winter sea-water characteristics at the northern coast of the Gulf of Aqaba, that is witnessing rapid development and increasing changes in its geomorphological characteristics. Sea-water temperature, salinity, nutrients, and chlorophyll a concentrations were measured biweekly at five coastal and four cross-sectional stations during the periods February to April and July to September 2004. Meteorological conditions were continuously recorded at the Marine Science Station. The coastal study sites included four open coastal stations and a marina with one-way exchange with the open water. The effect of convective mixing was clearly apparent on the sea-water characteristics. Natural seasonal characteristics of higher nutrients and chlorophyll a concentrations were recorded during winter at most of the open coastal stations. In the cross-sectional stations, the concentrations of nutrients and chlorophyll a were not different between the surface and the bottom during winter, but the bottom waters had generally higher concentrations during summer. Some deviations from the natural seasonal cycle were recorded at the marina and other coastal stations. Here, higher nutrient and chlorophyll a concentrations were recorded in summer than in winter. These deviations that are most likely due to anthropogenic effects are discussed.     

A century-long trend of metal pollution in the Sheyang River,on the coast of Jiangsu (China), reconstructed from sedimentary record

In order to reveal the historical context of metal element accumulation under the economic boom during the last decades in eastern China, concentrations of nine metal elements, radionuclides (²¹⁰Pb), Pb isotope ratios (²⁰⁷Pb/²⁰⁶Pb) and sedimentary characteristics were investigated in two sediment cores collected from the Sheyang River. The sediments have recorded the heavy metal deposition and thus allow establishing a connection between the temporal evolution of the heavy metal pollution and historical changes in industrial and urban discharges. Enrichment factors (EFs) were calculated to estimate the level of contamination in these sediments. A significant anthropogenic enrichment of Cu, Ni, Pb, Cr and Zn was highlighted, which were identified from anthropogenic discharges from cities and industrial sources, according to a cluster analysis. According to the annual variation in GDP growth rate, industrial growth rate, ratio of ²⁰⁷Pb/²⁰⁶Pb and EFs, it was obvious that sedimentary accumulation of metals has a close relationship with anthropogenic activities. In the pre-industrial period, natural inputs prevailed with lower EF and constant ²⁰⁷Pb/²⁰⁶Pb ratios around 0.82. However, during 1980–1995, the rapid industrial development caused a gradual increase in EFs and ²⁰⁷Pb/²⁰⁶Pb (>0.83). Our results disinterred the evolution of anthropogenic metal inputs in the last century into the Sheyang River.     

Modified dehydrogenase enzyme assay for evaluation of the influence of Hg,Cd, and Zn on the bacterial community structure of a wastewater treatment plant

In this study, a traditional assay was modified to evaluate the effect of Hg, Cd, and Zn on the bacterial community of a sequencing batch reactor and activated sludge plants and heavy metal-resistant bacterial species were determined. After the isolation of metal-resistant bacteria, their 16S rRNA gene fragments were sequenced. The BLAST program was used to compare the resulting 16S rRNA sequences with those in GenBank database to identify the isolated bacterial species. Hg was found to be the most toxic metal for both bacterial communities investigated. Sequence batch reactor bacteria were comparatively more resistant to Hg, Cd, and Zn than those from activated sludge. The resistant strains were close to the members of genus Pseudomonas, Kocuria, Stenotrophomonas, Enterococcus, and Staphylococcus. The modified dehydrogenase enzyme assay seems to be simple, robust, and competent for evaluation of the impact of metals on bacterial activity. Sequencing batch reactor systems should be preferred over activated sludge when wastewaters containing hazardous metals are to be treated.     

A same-sex stepparent shortens a prebreeder's duration on the natal territory: tests of two hypotheses in Florida scrub-jays

Prebreeders of the Florida scrub-jay (Aphelocoma coerulescens) are less likely to be found on their natal territories with a same-sex stepparent than with parents or an opposite-sex stepparent. We tested two models that had been proposed to account for this sexual asymmetry. The dominance hypothesis states that stepparents perceive same-sex prebreeders as competitors, primarily for a mate, so behave aggressively toward them. The pair-formation hypothesis states that prebreeders remain home to pair eventually with the opposite-sex stepparent. Predictions from these two models were tested by analyses from a quarter-century of records on a study population at Archbold Biological Station and by new behavioral field observations at the Station. Results clearly rejected the latter and strongly supported the former hypothesis. No prediction from the pair-formation hypothesis was confirmed: no pairing by a prebreeder of either sex has ever occurred with a stepparent; remaining home was equally frequent in age-one males with stepmothers and genetic mothers, and in females with stepfathers and genetic fathers; and the same results were found in age-two prebreeders. By contrast, the data strongly supported the dominance hypothesis. Field data showed higher aggression rates by stepfathers to male prebreeders and stepmothers to female prebreeders than by parents to their same-sex genetic offspring. Fewer age-one males remained home with a stepfather than with the genetic father, and the same was found for age-one females with a stepmother and genetic mother; at age two, the effect occurred only in female prebreeders. The two hypotheses make different predictions about prebreeders with two stepparents versus with both parents, thus providing a critical test. The dominance hypothesis correctly predicted decreased duration at home by age-one males and females; data for age-two females were in the direction of predicted difference but not significant; and, as in other tests, no effect was found for age-two males. We propose that age-two male prebreeders remain home despite elevated aggression from stepfathers because these prebreeders retain the possibility of budding from or inheriting the natal territory. Received: 16 July 1997 / Accepted after revision: 26 June 1998     

A neural network experiment on the simulation of daily nitrate-nitrogen and suspended sediment fluxes from a small agricultural catchment

In this paper, we report an application of neural networks to simulate daily nitrate-nitrogen and suspended sediment fluxes from a small 7.1 km² agricultural catchment (Melarchez), 70 km east of Paris, France. Nitrate-nitrogen and sediment losses are only a few possible consequences of soil erosion and biochemical applications associated to human activities such as intensive agriculture. Stacked multilayer perceptrons models (MLPs) like the ones explored here are based on commonly available inputs and yet are reasonably accurate considering their simplicity and ease of implementation. Note that the simulation does not resort on water quality flux observations at previous time steps as model inputs, which would be appropriate, for example, to predict the water chemistry of a drinking water plant a few time steps ahead. The water quality fluxes are strictly mapped to historical mean flux values and to hydro-climatic variables such as stream flow, rainfall, and soil moisture index (12 model input candidates in total), allowing its usage even when no flux observations are available. Self-organizing feature maps based on the network structure established by Kohonen were employed first to produce the training and the testing data sets, with the intent to produce statistically close subsets so that any difference in model performance between validation and testing has to be associated to the model and not to the data subsets. The stacked MLPs reached different levels of performance simulating the nitrate-nitrogen flux and the suspended sediment flux. In the first instance, 2-input stacked MLP nitrate-nitrogen simulations, based on the same-day stream flow and on the 80-cm soil moisture index, have a performance of almost 90% according to the efficiency index. On the other hand, the performance of 3-input stacked MLPs (same-day stream flow, same-day historical flux, and same-day stream flow increment) reached a little more than 75% according to the same criterion. The results presented here are deemed already promising enough, and should encourage water resources managers to implement simple models whenever appropriate.     

Using a fisheries ecosystem model with a water quality model to explore trophic and habitat impacts on a fisheries stock: A case study of the blue crab population in the Chesapeake Bay

Recent calls for the development of ecosystem-based fisheries management compel the development of resource management tools and linkages between existing fisheries management tools and other resource tools to enable assessment and management of multiple impacts on fisheries resources. In this paper, we describe the use of the Chesapeake Bay Fisheries Ecosystem Model (CBFEM), developed using the Ecopath with Ecosim (EwE) software, and the Chesapeake Bay Water Quality Model (WQM) to demonstrate how linkages between available modeling tools can be used to inform ecosystem-based natural resource management. The CBFEM was developed to provide strategic ecosystem information in support of fisheries management. The WQM was developed to assess impacts on water quality. The CBFEM was indirectly coupled with the WQM to assess the effects of water quality and submerged aquatic vegetation (SAV) on blue crabs. The output from two WQM scenarios (1985-1994), a baseline scenario representing actual nutrient inputs and another with reduced inputs based on a tributary management strategy, was incorporated into the CBFEM. The results suggested that blue crab biomass could be enhanced under management strategies (reduced nutrient input) when the effective search rate of blue crab young-of-the-year's (YOY's) predators or the vulnerability of blue crab YOY to its predators was adjusted by SAV. Such model linkages are important for incorporating physical and biological components of ecosystems in order to explore ecosystem-based fisheries management options.