Adjacent Coastal Environments Research Articles

Multi-annual and multi-decadal evolution of sediment accretion in a saltmarsh of the French Atlantic coast: Implications for carbon sequestration

Coastal marshes offer natural solutions for adapting to and mitigating the effects of climate change and sea level rise. However, the resilience of the marsh physical system and, with it, the ecosystem services that it provides, is largely site specific. This calls for the increase in the spatial cover of coastal marsh studies in order to assess the controlling factors of marsh evolution, and their long-term carbon storage capacities. Here, we study the spatio-temporal variations in sedimentation rates and organic carbon (OC) sequestration capacity of the macrotidal minerogenic saltmarshes in Aiguillon Bay, belonging to one of the largest French coastal marshes. Supported by aerial photographs and satellite image analysis, we first show that saltmarshes of the Aiguillon Bay have prograded at very high rates, up to 14 m yr−1 since 1950. Sediment accumulation rates (SAR) were estimated at both multi-annual to multi-decadal scales based on two approaches: (i) LiDAR-based digital elevation models from multiple acquisition dates (2010–2021); and (ii) depth profiles of 210Pb in excess and 137Cs in sediment cores collected along cross-shore transects in the saltmarshes. Long-term SAR range from 0.8 to 2.2 cm yr−1 and are among the highest reported worldwide for equivalent systems. The positive accretion balance (accretion rate minus local sea-level rise rate) provides important clues on marsh resilience suggesting that the Aiguillon Bay is currently able to adapt to rising sea level. Despite relatively low organic carbon content (1.3–6.0%), high SAR leads to high carbon sequestration rates (99–345 gC m−2 yr−1; or a mean value of 2.5 Mg C ha−1 yr−1). The isotopic signature of sediment OC reveals a significant and rapid decomposition of organic material in surface cores, while allochthonous sediment of marine origin dominates the signature of chemically-stable OC of marsh sediments. This implies that the carbon sequestration capacity of minerogenic saltmarshes, such as those of the Pertuis Charentais, also depends upon the wealth of adjacent coastal environments through high sediment supply and primary productivity.

Conversion of Forest to Agriculture Increases Colored Dissolved Organic Matter in a Subtropical Catchment and Adjacent Coastal Environment

AbstractLand‐ocean dissolved organic matter (DOM) transport is a significant and changing term in global biogeochemical cycles which is increasing as a result of human perturbation, including land‐use change. Knowledge of the behavior and fate of transported DOM is lacking, particularly in the tropics and subtropics where land‐use change is occurring rapidly. We used Parallel Factor (PARAFAC) Analysis to investigate how land‐use influenced the composition of the DOM pool along a subtropical land‐use gradient (from near‐pristine broadleaf forest to agri‐urban settings) in Belize, Central America. Three humic‐like and two protein‐like components were identified, each of which was present across land uses and environments. Land‐use mapping identified a strong (R2 = 0.81) negative correlation between broadleaf forest and agri‐urban land. All PARAFAC components were positively associated with agri‐urban land‐use classes (cropland, grassland, and/or urban land), indicating that land‐use change from forested to agri‐urban exerts influence on the composition of the DOM pool. Humic‐like DOM exhibited linear accumulation with distance downstream and behaved conservatively in the coastal zone whilst protein‐like DOM exhibited nonlinear accumulation within the main river and nonconservative mixing in coastal waters, indicative of differences in reactivity. We used a hydrodynamic model to explore the potential of conservative humics to reach the region's environmentally and economically valuable coral reefs. We find that offshore corals experience short exposures (10 ± 11 days yr−1) to large (∼120%) terrigenous DOM increases, whilst nearshore corals experience prolonged exposure (113 ± 24 days yr−1) to relatively small (∼30%) terrigenous DOM increases.

Will flooding or erosion of historic landfills result in a significant release of soluble contaminants to the coastal zone?

Historically, solid wastes were commonly landfilled in the coastal zone in sites with limited engineering to isolate waste from adjacent coastal environments. Climate change is increasing the likelihood that these historic coastal landfills will be inundated or eroded resulting in the release of soluble contaminants to the coastal zone. Previously research has focussed on the environmental impacts of leaching from landfills in freshwater environments with little or no consideration being given to saline environments. This research investigated the magnitude, variability and potential environmental consequences of soluble metal release from solid wastes when historic coastal landfills are inundated, or wastes are eroded and released into fresh or saline waters. The proportions of the sites' total metal contents released to solution varied by up to an order of magnitude between different landfills due to the different physical and chemical characteristics of the solid wastes, but the proportions released were typically ≪1% in freshwater. Inundation by saline water significantly increases the proportions of the total metal contents released to solution, e.g. 5450% more Pb in one study site (median value), but again the proportions were typically ≪1%. The exception was Cd, where up to 9% of the total Cd load of one site was released in saline water. This puts into question the suitability of current landfill regulatory tests, e.g. the EU Waste Acceptance Criteria, and many risk assessment methods, which only consider freshwater inundation and leaching. However, the very low proportions of metals mobilised from the solid waste and the high dilution ratios in coastal waters, mean EQSs for the Protection of Surface Water are unlikely to be exceeded, and the release of solid wastes through coastal erosion poses a greater threat to coastal ecological health than leaching of soluble metals from contained solid wastes.

Potential contamination of the coastal zone by eroding historic landfills

Historically solid waste was commonly landfilled in the coastal zone in sites with limited engineering to isolate waste from adjacent coastal environments. Climate change is increasing the likelihood that these historic coastal landfills will erode releasing solid waste to the coastal zone. Historic coastal landfills are frequently located near designated ecological sites; yet, there is little understanding of the environmental risk posed by released waste. This research investigated inorganic and organic contaminant concentrations in a range of solid waste materials excavated from two historic coastal landfills, and the potential ecological impact should eroded waste be released to the coastal environment. Contaminant concentrations in the analysed waste materials exceeded sediment quality guidelines, indicating erosion of historic coastal landfills may pose a significant environmental threat. Paper and textile wastes were found to make a significant contribution to the total contaminant load, suggesting risk assessments should consider a wide range of solid waste materials.

Seasonal variability of 7Be in suspended sediments from the Copper River, Alaska: implications for quantifying recent flood deposits in coastal environments

Over the past three decades, particle-reactive cosmogenic 7Be (t1/2 = 53.3 d) has frequently been used to quantify recent fluvial sediment inputs to estuaries and coastal marine environments, providing an important tool to understand the timing and pathways of sediment dispersal. This study utilizes a 2-year high-resolution time series collected from the Copper River, Alaska, to examine the seasonal fluctuation in 7Be activity of suspended sediments near the river mouth. We show that there is considerable variability (particulate 7Be = ≤ 3.3–47 Bq kg−1) throughout the hydrograph, with a significant negative correlation to discharge and suspended sediment concentration. This variability is interpreted to be driven by a combination of fluctuations in atmospheric deposition, water aging, and dilution by 7Be-depleted sediments, reflecting erosion within the streambed/watershed and/or differing freshwater/sediment source. Particularly within this high-latitude setting, seasonal differences in provenance (snowpack/glacial melting vs. rainfall) likely influence 7Be activities. Importantly, 7Be was below detectable limits in river suspended sediments during peak discharge periods in both years, indicating that the flood signal in adjacent coastal environments will be negligible at this time. These results suggest that 7Be will not be an effective tracer of fluvial sediment deposition in some coastal environments.

Post-catastrophe Analysis of the Fundão Tailings Dam Failure in the Doce River System, Southeast Brazil: Potentially Toxic Elements in Affected Soils

On November 5, 2015, after the collapse of the Fundao tailings dam, a massive amount of iron mine waste was released into the Doce River system in southeast Brazil. The aim of our study was to determine the mass fractions of potentially toxic elements in soil affected by the deposition of material by the waste wave. A preliminary screening was performed with portable X-ray fluorescence spectrometry (PXRF) and principal component analysis (PCA). The EPA 3050B method was further applied to digest the samples for quantitative determination of As, Ba, Cr, Cu, Mn, Ni, Pb, V, and Zn by inductively coupled plasma mass spectrometry. PCA was useful to classify the mine waste samples based on the Fe signal from the PXRF spectra, in spite of the heterogeneous nature of the material discharged into the Doce River system. The anomalous levels of As (up to 164 mg kg−1) and Mn (as high as 2410 mg kg−1) found in some mine waste and affected soil samples are within the background ranges typically observed in the soils of the Iron Quadrangle region. The toxicity characteristic leaching procedure shows no evidence of hazards regarding As, but a high natural background level of Mn was found in the mobile fraction. This preliminary environmental assessment highlights the importance of evaluation of long-term effects on soil directly impacted, as well as on the aquatic biota of the Doce River system and adjacent coastal environment given the large affected area, which includes regions with varying background levels of toxic elements.

Nutrient characterisation of river inflow into the estuaries of the Gouritz Water Management Area, South Africa

This study provides an overview of the nutrient status of river inflow into the estuaries within the Gouritz Water Management Area (WMA) of South Africa. Riverine inputs are a major source of macronutrients to estuaries and the adjacent coastal environments. Long-term water quality monitoring data (dissolved inorganic nitrogen, i.e. DIN; and dissolved inorganic phosphorus, i.e. DIP), collected by the Department of Water Affairs (DWA), were used to assess historical trends of river nutrient inflow within the Gouritz WMA. The results indicate that DIP concentrations exceeded the eutrophic limits for aquatic ecosystems (DWA) in 50% of the catchments assessed. Anthropogenic activities such as agriculture, wastewater discharge, urbanisation, and afforestation were significant factors influencing nutrient levels within these rivers. For the majority of the river systems (approx. 80%) there was no significant correlation (P > 0.05) between inorganic nutrient levels and freshwater inflow from the catchments. Wastewater treatment plant (WWTP) data (DWA) were assessed to explore the reasons for this ‘disconnect’ between freshwater inflow and inorganic nutrient levels. Results indicate that the Gwaing (267.73 kg·d-1 DIN; 77.46 kg·d-1 DIP), Goukou (49.71 kg·d-1 DIN; 17.38 kg·d-1 DIP), Knysna (41.77 kg·d-1 DIN; 13.92 kg·d-1 DIP) and Hartenbos (37.73 kg·d-1 DIN; 21.39 kg·d-1 DIP) systems received the highest daily loads from WWTPs. The Gwaing and Hartenbos estuaries would be most vulnerable to increased nutrient loading because of their small size and prolonged periods of mouth closure. The study highlights the importance of water quality monitoring of river inflows into coastal ecosystems, as it is needed to assess pollution trends and identify management priorities.Keywords: Water quality, eutrophication, inorganic nutrients, wastewater discharges

Studies of Decomposition rate and release of nutrients Ammonium, Nitrates, Nitrites, and Phosphatesions during the decomposition of Oryza coarctata in the laboratory experiment.

he vegetation, other than the mangroves in Indus delta, for example Oryza coarctata is also the source of nutrients for the adjacent coastal environment. The O. coarctata is the major vegetation on the tidal mudflatds of Keti- Bunder (Hajambro creek), Indus delta, other than the Avicennia marina and Rhizophora mucronataplanted mangrove forest. This is the first report of decomposition rates of O. coarctata in the laboratory. The decomposition of O. coarctata. was conducted to evaluate the nutrients (ammonium, nitrate, nitrites, phosphates) during the decomposition. The decomposition rate was more rapid during this early phase and O. coarctata. decomposed up to 40 % during the first 7 days. Afterwards, the Oryzasp. decomposed slowly and gradually and remained up to 40% of the dry mass. Therefor e, about 60% of the organic matter present in the O. coarctatacan decompose completely in the aerobic conditions of the aquatic environment. The ammonium ions concentration was found 2.75 μM/L at 7th day and highest value was 6.38 μM/L at 124th day of exp eriment. So the amount of ammonium ions increased during the phase of decomposition. The nitrate ions concentration was 1.95 μM/L at 7th day and increased to 2.71 μM/L at 15th day of decomposition, and afterwards the concentration of nitrate decreased gradually and lowest value 0.129 μM/L was recorded in the last day of the experiment. The nitrite ions concentration was found 1.80 μM/L and gradually increased to 3.33 μM/L at 60th day and the lowest value was 3.05 μM/L. The initial concentration of the phosphate ions was 0.84 and decresed gradually during the phase of decomposition to its lowest value at 0.7 μM/L. The concentration of the nitrogen in the O. coarctata was initially between 1- 1.5 mg DW, which increased to about 2 mg DW at the 7th day of the decomposition. The % DW nitrogen contents than decreased suddenly at 15th day reaching up to about 1 mg DW of the decomposed material. This decrease of the t otal DW Nitrogen is very important, as it is the source of the nutrients to the adjacent ecosystem. The results are also strongly correlated with the nutrients values.

Effects of land use change and sediment mobilization on coastal contamination (Coatzacoalcos River, Mexico)

Coastal ecosystems are subject to many anthropogenic pressures, including pollution and the enhancement of sedimentation due to human activities. The lower reach of the Coatzacoalcos River is considered to be the most polluted coastal area of Mexico due to the presence of major petrochemical production centers in its watershed. In order to show the impact of land use change and industrial activities on the adjacent coastal environment of the Coatzacoalcos River, we reconstructed the historical changes of sediment transport and trace metals contamination based on the study of a 210Pb dated sediment core. Several geochemical indicators, such as clay mineral content, the concentrations of reference elements (Al, Ca, Sr, Rb) and the carbon isotope ratio (δ13C) revealed a change of sediment and contamination sources since the early 80s, in coincidence with the large industrial and urban development in the area. We conclude that the increased contaminant loads were related to terrestrial sources, likely contaminated and eroded soils from the catchment, due to extensive land use changes. Although the contaminant enrichment since the early 80s was low, As, Hg and Ni concentrations show potentially dangerous levels and exceed the USEPA-ERL concentration benchmarks, thus constituting a potential threat to marine aquatic life and humans through seafood consumption.

Diel Aquatic CO2 System Dynamics of a Bermudian Mangrove Environment

Mangrove ecosystems play an important, but understudied, role in the cycling of carbon in tropical and subtropical coastal ocean environments. In the present study, we examined the diel dynamics of seawater carbon dioxide (CO2) and dissolved oxygen (DO) for a mangrove-dominated marine ecosystem (Mangrove Bay) and an adjacent intracoastal waterway (Ferry Reach) on the island of Bermuda. Spatial and temporal trends in seawater carbonate chemistry and associated variables were assessed from direct measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen (DO), temperature, and salinity. Diel pCO2 variability was interpolated across hourly wind speed measurements to determine variability in daily CO2 fluxes for the month of October 2007 in Bermuda. From these observations, we estimated rates of net sea to air CO2 exchange for these two coastal ecosystems at 59.8 ± 17.3 in Mangrove Bay and 5.5 ± 1.3 mmol m?2 d?1 in Ferry Reach. These results highlight the potential for large differences in carbonate system functioning and sea-air CO2 flux in adjacent coastal environments. In addition, observation of large diel variability in CO2 system parameters (e.g., mean pCO2: 390–2,841 ?atm; mean pHT: 8.05–7.34) underscores the need for careful consideration of diel cycles in long-term sampling regimes and flux estimates.

The influence of conceptual model uncertainty on management decisions for a groundwater-dependent ecosystem in karst

Summary Groundwater management in karst is often based on limited hydrologic understanding of the aquifer. The geologic heterogeneities controlling the water flow are often insufficiently mapped. As karst aquifers are very vulnerable to pollution, groundwater protection and land use management are crucial to preserve water resources and maintain ecosystem services. Multiple Model Simulation highlights the impact of model structure uncertainty on management decisions using several plausible conceptual models. Multiple Model Simulation was used for this purpose on the Yucatan Peninsula, which is one of the world’s largest karstic aquifers. The aquifer is the only available fresh water source for human users and ecosystems on the Peninsula. One of Mexico’s largest protected areas, the groundwater-dependent Sian Ka’an Biosphere Reserve (5280 km 2 ) is fed by the aquifer’s thin freshwater lens. Increasing groundwater abstractions and pollution threatens the fresh water resource, and consequently the ecosystem integrity of both Sian Ka’an and the adjacent coastal environment. Seven different catchment-scale conceptual models were implemented in a distributed hydrological modelling approach. Equivalent porous medium conceptualizations with uniform and heterogeneous distributions of hydraulic conductivities were used. The models demonstrated that Sian Ka’an’s wetlands are indeed groundwater-fed. The water quantities in the wetlands and the flooding dynamics are determined by the larger groundwater catchment. The overall water balance for the model domain showed that recharge constitutes 4400 ± 700 million m 3 /year. Of this, 4–12% exits as overland flow, and 88–96% exits as groundwater flow. Net groundwater outflow from the model domain to the north via the Holbox fracture zone appears as an important cross-basin transfer between regions of the Peninsula. Probability maps of Sian Ka’an’s catchment were obtained through automatic calibration and stochastic modelling. Groundwater travel time zones were calculated based on different calibrated effective porosities. The spatial modelling results highlight the impact of regional-scale structures on the flow field and transport times.

Review of Countermeasures against Beach Erosion on the Taiwanese Coast

Beach erosion is one of the most significant coastal preservation problems in the world. This study first briefly addresses the influences of human activity on beach erosion. The seriousness of beach erosion in Taiwan has received considerable attention since the 1960s, following rapid population growth and economic development in the coastal areas. Hard solutions of stabilized structures against beach erosion in Taiwan at that time are reviewed based on their effectiveness in protecting property and their ability to produce a landscape that harmonizes with the adjacent coastal environment. Soft coastal defense solutions implemented recently in coastal regions in Taiwan are introduced and their benefits are discussed. This study concludes that various methods designed to prevent wave- and current-induced beach erosion should be based on analyses of nearshore hydrodynamics, sediment transport, coastal processes, and physiographic features of beaches.

A synthesis of dominant ecological processes in intensive shrimp ponds and adjacent coastal environments in NE Australia

One of the key environmental concerns about shrimp farming is the discharge of waters with high levels of nutrients and suspended solids into adjacent waterways. In this paper we synthesize the results of our multidisciplinary research linking ecological processes in intensive shrimp ponds with their downstream impacts in tidal, mangrove-lined creeks. The incorporation of process measurements and bioindicators, in addition to water quality measurements, improved our understanding of the effect of shrimp farm discharges on the ecological health of the receiving water bodies. Changes in water quality parameters were an oversimplification of the ecological effects of water discharges, and use of key measures including primary production rates, phytoplankton responses to nutrients, community shifts in zooplankton and δ 15N ratios in marine plants have the potential to provide more integrated and robust measures. Ultimately, reduction in nutrient discharges is most likely to ensure the future sustainability of the industry.

Distribution and source recognition of polycyclic aromatic hydrocarbons in the sediments of Hsin-ta Harbour and adjacent coastal areas, Taiwan

Thirty-three sediment samples from Hsin-ta Harbour and neighboring coastal areas were analyzed by GC-MS for polycyclic aromatic hydrocarbons (PAHs). Total concentrations of 30 analyzed parental and alkylated PAHs (∑PAH) varied from 98.1 to 3382 ng/g dry weight. MP/P (methylphenanthrenes/phenanthrene) values larger than 2 coincided with very low P/A (phenanthrene/anthracene) values at inner harbour stations, revealing that a significant portion of low molecular weight PAHs are probably from petrogenic pollution sources, specifically, illegal disposal of used motor oil. The 4,6-dimethyldibenzothiophene/3,6-dimethylphenanthrene (4,6-C 2D/3,6-C 2P) ratio is found to be more useful than the MP/P ratio in tracing petrogenic PAHs from the inner harbour area to the adjacent coastal environment. In addition, according to hierarchical cluster analysis, collected sediments cluster in three major groups, Off-shore Group, Near-shore Group and Inner Harbour Group. Three diagnostic ratios, 4,6-C 2D/3,6-C 2P, PER/∑PAH (perylene to ∑PAH) and BaA/CHR (benzo( a)anthracene/chrysene), representing petrogenic, biogenic and pyrogenic origins, are found to be effective in differentiating and characterizing sediments among the groups in this study. Enrichment of pyrogenic and petrogenic PAHs in sediments collected exhibits mixing or dilution, spatially, by biogenic (or natural) PAHs.

Zn and Cd production and pollution in a Brazilian coastal region

The impact of a milling and smelting industry in the coastal region of Rio de Janeiro is evaluated based on production and environmental parameters. These approaches are compared using deposition rates in coastal sediments and emission factors from the industrial process. The disposal of industrial wastes has increased the deposition of Zn and Cd in the adjacent coastal environment by factors approximating 200-fold, and has altered the relationship between Zn and Cd in coastal sediments.

Holocene evolution of an estuarine coast and tidal wetlands

Research Article| March 01, 1990 Holocene evolution of an estuarine coast and tidal wetlands CHARLES H. FLETCHER, III; CHARLES H. FLETCHER, III 1Department of Geology and Astronomy, West Chester University, West Chester, Pennsylvania 19383 Search for other works by this author on: GSW Google Scholar HARLEY J. KNEBEL; HARLEY J. KNEBEL 2U.S Geological Survey, Woods Hole, Massachusetts 02543 Search for other works by this author on: GSW Google Scholar JOHN C. KRAFT JOHN C. KRAFT 3Geology Department, University of Delaware, Newark, Delaware 19716 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1990) 102 (3): 283–297. https://doi.org/10.1130/0016-7606(1990)102<0283:HEOAEC>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation CHARLES H. FLETCHER, HARLEY J. KNEBEL, JOHN C. KRAFT; Holocene evolution of an estuarine coast and tidal wetlands. GSA Bulletin 1990;; 102 (3): 283–297. doi: https://doi.org/10.1130/0016-7606(1990)102<0283:HEOAEC>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Modern facies-distribution patterns, extensive core data, and chronostratigraphic cross sections provide a detailed history of Holocene inundation within the Delaware Bay estuary and sedimentation in adjacent coastal environments. Flooding of the estuary occurred with rising sea level as the shoreline retreated northwest along a path determined by the pre-transgression topography. Simultaneous migration of an estuarine turbidity maximum depocenter provided the bulk of fine sediments which form the coastal Holocene section of the estuary. Prior to 10 Ka, the ancestral bay was predominantly a tidal river, and the turbidity maximum depocenter was located southeast of the modern bay mouth. By 10 Ka, lowlands adjacent to the ancestral channel of the Delaware River were flooded, forming localized tidal wetlands, and the depocenter had initiated high rates of fine-grained sedimentation near the present bay mouth. At that time, coastal Holocene strata began to onlap the interfluve highlands. By 8 Ka, the fine-grained depocenter had migrated northwest along the main channel of the Delaware River, although the widened mouths of tributary valleys continued to be active sites of sediment accumulation. Following the passage of the fine-grained depocenter, coarse-grained sediments accumulated along the coast in response to increased wind-wave activity. During the middle Holocene, portions of the estuarine coast began to resemble modern geomorphology, and washover barrier sands and headland beach sandy gravels accumulated along the southwest shore. The late Holocene was characterized by erosional truncation and submergence of aggraded coastal lithofacies and by planation of remnant highland areas. Knowledge of the eroded Holocene section is fragmentary. At present, continued sea-level rise is accompanied by deposition of tidally transported muds in coastal environments and deposition of sandy sediments in some offshore regions. An unconformity marks the base of the developing open estuarine sequence of coarse clastic lithofacies and denotes the end of coastal accumulations. Modeling of coastal-lithofacies transitions identifies specific lithofacies complexes in the Holocene stratigraphic section which were influential in the evolution of the coast. Development of the Holocene section of the estuary coast involved both constructive, or aggradational, and destructive, or erosional, phases. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Temporal and spatial variation in an island fish fauna

Elements of the reef fish fauna of a northeastern New Zealand island group was sampled over a 12-yr period. Sampling was divided into temporal and spatial elements. Temporal sampling in the form of annual surveys of labrid fishes was carried out at a single locality from 1974 until 1986. Surveys of a single species Suezichthys aylingi Russell were carried out from 1972 to 1986. Two series of surveys to analyse spatial pattern were carried out in 1982 and in 1984. The sampling targets were juvenile and adult rather than newly settled fishes. The degree of fluctuation in fish numbers over time reflected differences in geographic distribution and source areas amongst the different species. One element derived from northern subtropical areas declined from moderate numbers in 1974 to local extinction by 1979. The greatest numerical fluctuation (a 15-fold change) was observed in S. aylingi. Island populations of this species appeared to be derived from a discrete source area in northern New Zealand, the Three Kings Islands. Other species of labrids with established populations in northern New Zealand displayed moderate fluctuations. Labrids with southern distributions and abundant in adjacent coastal environments were rare at the islands and showed little variation in numbers. For most species, numerical fluctuations followed a similar course with enhanced numbers in the early 1970s, followed by marked decline, then showing a modest increase during the early 1980s. The patterns of numerical change correlated with both coastal sea temperatures and storm-induced disturbance to the habitat. The reef fish fauna showed marked spatial variation, often at very localized scales. Where temporal and spatial monitoring were combined the spatial patterns remained coherent over time. For most species examined spatial variation was of greater magnitude than temporal variation. We suggest that two mechanisms are involved. Inter-annual variation in numbers of recruits results from events in the oceanic environment of northeastern New Zealand. The spatial patterns were apparently driven by habitat selection at the settlement stage of reef fishes. Temporal variation appeared to enhance spatial patterns but not override them.

BEACH HAVEN AND LITTLE EGG INLETS, A CASE STUDY

A comprehensive investigation of coastal processes active within and in the vicinity of Beach Haven and Little Egg Inlets was completed as part of the Coastal Processes Investigation for the proposed Atlantic Generating Station. The suspected complex nature of this dual natural inlet system was documented and a process-response model is presented to relate the more significant physical forcing functions to observed morphologic and hydraulic changes. A rising sea level, a net littoral drift from the north and the sediment scouring power of the flow in the two main channels serving the tidal basins are the principal factors related to the geographic and hydraulic stability of the system. The results of the study can be used to evaluate the potential impact, if any, of the proposed Atlantic Generating Station on the adjacent coastal environment.

The demersal fish of Narragansett Bay: An analysis of community structure, distribution and abundance

Monthly samples of demersal fish were collected from nine regular and 13 occasional stations in Narragansett Bay, Rhode Island throughout a year. While over 9000 individuals representing 99 species were taken, the 10 most abundant species made up 91% of the catch. Taxonomic composition and dominance of the fish community were generally similar to that reported for adjacent Block Island Sound and Long Island Sound, though diversity was slightly higher in the bay. Winter flounder, Pseudopleuronectes americanus was by far the most abundant species, and accounted for 36% of the total catch. Multiple regression analysis of fish numbers and biomass for total catch and for the dominant flounder indicated that of 14 environmental variables considered, only depth, sediment organic content, temperature and wind speed were significant in explaining distribution within the bay. No clear pattern of fish abundance was apparent, except for higher diversity near the mouth of the bay. The mean annual standing crop of 117 ± 151 fish/acre and 28·5 ± 16·0 lbs/acre (wet weight) was comparable to values reported for a variety of New England coastal and offshore areas. The total biomass of fish remained remarkably constant throughout the year when compared to adjacent coastal environments, while the abundance of particular species varied substantially with season.