Nearshore Coastal Waters Research Articles

Nutrient, chlorophyll, and water clarity relationships in Florida's nearshore coastal waters with comparisons to freshwater lakes

Models relating chlorophyll to nutrients and Secchi depth to chlorophyll using data from nearshore coastal waters of Florida were successfully developed. The models suggest that phosphorus is the primary limiting factor for phytoplankton in the nearshore coastal waters of Florida and that total phosphorus concentration accounts for 81% of the variance in chlorophyll concentration. The models also show that chlorophyll is the dominant factor determining Secchi depth in nearshore coastal waters of Florida and that chlorophyll concentrations account for 68% of the variance in Secchi depth. Thus, these models are robust and should be useful for eutrophication management of Florida's coastal marine systems. The models developed with data from nearshore coastal waters of Florida are similar to models developed for freshwater lakes in Florida, but the amount of chlorophyll per unit of phosphorus and Secchi depth per unit of chlorophyll are both significantly less for marine samples. This suggests that the chlorophyll to biovolume ratios in the nearshore coastal waters of Florida are less than in freshwater systems of Florida. Therefore, nutrient to chlorophyll and chlorophyll to Secchi depth models developed for freshwater systems are probably ill suited for use in Florida's marine systems.

The Management of Contaminated Sediment in Hong Kong

Many years of uncontrolled discharge of sewage and industrial effluent have resulted in serious contamination of much of the sediments underlying inland and nearshore coastal waters in Hong Kong by potentially toxic heavy metal and trace organic pollutants. Much has been achieved to improve control of this pollution at the source and prevent further deterioration. Nevertheless, comprehensive environmental assessment and management measures are required to ensure that any unacceptably contaminated sediment that must be dredged to facilitate infrastructural development is safely handled and disposed of.It is estimated that some 50 Mm3 of sediment classified as unacceptably contaminated may require dredging and special management elsewhere over the coming 10-year period. To facilitate improved decision making about the most appropriate disposal options for dredged sediment Hong Kong has recently implemented a new sediment quality assessment framework under which information on the biological activity of contaminated material is considered in addition to data on chemical composition.Dredged sediment classified as unacceptably contaminated has been disposed of at a contained disposal facility at East Sha Chau since 1992. To date over 20 Mm3 of sediment has been placed into seabed pits that are subsequently capped with clay. The site is subject to a rigorous monitoring programme that has clearly demonstrated its environmental acceptability.

Horizontal Trends in Larval Fish Diversity and Abundance Along an Ocean-Estuarine Gradient on the Northern KwaZulu-Natal Coast, South Africa

The structure of the larval fish assemblages along an ocean-estuarine gradient in the St Lucia region on the northern KwaZulu-Natal coast of South Africa was examined using a combination of univariate, distributional and multivariate techniques. The data was comprised of a full annual set of ichthyoplankton samples taken from three types of environment: nearshore coastal waters, surf zone and within the St Lucia Estuary itself. The mean monthly densities of each species in each environment were used in the species matrix, and the mean monthly values of salinity, temperature and turbidity were used in the physical variables matrix. The mean species diversity and eveness index was significantly higher in the nearshore waters than the surf zone and estuary. The patterns of relative species abundances in each environment (K-dominance curves) showed that the estuarine environment was dominated by a few species in large numbers, the surf zone was intermediate, and the nearshore coast was the most diverse. Classification and multidimensional scaling (MDS) ordination analyses of larval fish densities grouped together into three main clusters based on the three different environments. The species similarity matrix (inverse analysis) clustered into four groups at the 10% similarity level. The MDS analysis of the same matrix showed that the groups separated out more or less according to the type of environment they occur in, and hence the level of estuarine dependence of the various species. Species belonging to each assemblage showed similarities with regards to their reproduction modes and/or preference to a particular physical condition. Some species were restricted to one environment, whilst others were common to two or all three environments. The occurrence of partially estuarine-dependent species in all three environments suggests that ocean-estuarine coupling is an important process for the recruitment success of these species. The ‘best fitting’ physical variable which explained the larval fish community patterns was turbidity on its own, with the relationship of larval densities to the physical variables being species-specific. The present study indicates that a number of factors must play a role in determining the structure and composition of larval fish assemblages occurring in different types of environments along an ocean-estuarine gradient. It is suggested that these distinct assemblages might be considered indicators for the different environments which they inhabit.

Winter mortality, growth, and behavior of young-of-the-year of four coastal fishes in New Jersey (USA) waters

Winter mortality has been hypothesized to select for large body size in young-of-the-year (YOY) fishes, yet substantiation of winter mortality and its cause(s) are available for few estuarine or marine species. We examined seasonal length distributions of wild populations of four common marine species, black sea bass (Centropristis striata), tautog (Tautoga onitis), cunner (Tautogolabrus adspersus), and smallmouth flounder (Etropus microstomus), and mortality (i.e., frequency of death), growth, and behavior of their YOY in the laboratory at ambient winter temperatures (mean 7°C, range 2–13°C) during a 135-day period (December 1992 through mid-April 1993) to establish potential causes of their mortality in the field. Young-of-the-year black sea bass experienced 100% mortality when water temperatures decreased to 2–3°C in February, emphasizing the importance of winter emigration from estuaries in this southern species. The low mortality of two labrid species, YOY tautog (14%) and YOY cunner (3%), was consistent with their northern distribution and year-round occurrence in estuarine and nearshore coastal waters. Laboratory mortality of YOY smallmouth flounder (33%) was higher for small (<35 mm total length) fish, suggesting that this small species may experience high winter mortality in estuaries and nearshore coastal waters. Seasonal differences in fish length result potentially from several mechanisms (e.g., mortality and/or migration) that are difficult to assess, but our laboratory experiments suggest that seasonal temperature changes cause size-specific mortality of YOY smallmouth flounder and offshore migration of YOY black sea bass.

Assessing the dispersal and exchange of brachyuran larvae between regions of San Diego Bay, California and nearshore coastal habitats using elemental fingerprinting

Marine benthic invertebrate populations found in estuarine or coastal habitats often exchange larvae. However, the dynamics of larval exchange are poorly understood because of difficulties in (1) making synoptic assessments of horizontal and vertical larval distribution patterns over large areas for extended periods of time and (2) determining the origins of field-sampled larvae. This study examines how temporal changes in the vertical and horizontal distribution of crab larvae (i.e., Pachygrapsus crassipes and Lophopanopeus spp.) affect larval transport. Larval concentration and water velocity data were collected concurrently and were used to estimate larval exchange between regions of San Diego Bay (SDB) and between SDB and nearshore coastal waters. A larval fingerprinting technique was used to distinguish SDB and non-SDB spawned, stage I P. crassipes zoeae to quantify larval exchange between SDB and nearshore coastal waters. First order estimates of larval exchange over a tidal cycle between inner and outer regions of SDB and between the bay and nearshore coastal habitats corroborate a net transport of stage I P crassipes zoeae from SDB as inferred from larval behavior. The estimated net larval exchange of Lophopanopeus spp. zoeae was into SDB, suggesting retention within the bay through larval development. Trace elemental fingerprinting of stage I P. crassipes zoeae revealed bi-directional exchange between SDB and the nearshore coastal environment when the predominant transport predicted from zoeal swimming behavior was out of San Diego Bay. Approximately 5% of stage I P crassipes zoeae sampled in the mid region of SDB originated from outside SDB, while 26% of zoeae sampled at the entrance originated from outside SDB. Combined use of trace elemental fingerprinting and synoptic field sampling techniques will help improve our understanding of larval transport and ultimately the population dynamics of nearshore species.

The Larval Fish Assemblage in Nearshore Coastal Waters off the St Lucia Estuary, South Africa

This paper reports on the composition, abundance and distribution of the larval fish assemblage in the nearshore coastal waters off the St Lucia Estuary mouth, South Africa. Ichthyoplankton samples were collected over a 12 month period from five stations located along a transect up to 2·5km offshore, and from two stations north and south of the estuary mouth, respectively. In all, 6126 fish larvae, representing 89 families and 186 species, were collected. Larvae in the families Myctophidae and Tripterygiidae comprised 21% and 16% of the total catch, respectively. The most abundant species were an unidentified triplefin, Tripterygiid 1 and the lanternfish Benthosema fibulatum, together which contributed nearly 18% of the total catch. Larvae of marine spawners independent of estuaries dominated the catch both in terms of density (90%) and in terms of number of taxa (89%). Some larvae of estuarine-associated species were present, in addition to a few specimens of estuarine resident species. Overall the dominant environmental variable affecting larval densities was temperature, particularly for Trypterygiid 1 where temperature contributed to 9% of the variance model. Densities of fish larvae peaked in November and December 1990 (late spring and early summer) and were lowest from January to June 1991 (summer, autumn an early winter). Different taxa dominated the catch each month with reef- and shelf-associated species accounting for the peak in August and September 1990, oceanic species in November 1990 and a mixture of the two groups in December. Overall larval densities were significantly higher in bottom samples with a trend of increasing densities offshore for reef and shelf taxa. The larvae of reef and shore taxa were predominantly preflexion larvae, whilst the few estuarine spawner species that were collected were mainly postflexion. Ontogenetic patterns related to depth and distance offshore were evident for the dominant species in each estuarine-association category.The present study has shown that temporal and spatial variations in the larval fish assemblage off St Lucia are related to environmental conditions and ontogenetic behavioural patterns of certain species. The origin of many of the larvae in the assemblages off the coast of St Lucia is probably from both local spawning populations in the shelf waters off KwaZulu-Natal and spawning populations farther north in shelf waters off Mozambique. Additional studies with more detailed oceanographic measurements will further our understanding of the physical processes that supply larvae to the St Lucia region.

Faecal indicator impacts on recreational waters: budget studies and diffuse source modelling

A series of investigations are underway which have quantified the contribution of faecal indicators delivered to nearshore coastal waters from the sewerage system and riverine inputs. Studies have been completed in Jersey, Staithes, Yorkshire, South Wales and the North-west. The research protocols have involved quantification of high and low flow faecal indicator delivery from the sewerage system and riverine sources as well as construction of nonpoint source models designed to predict faecal indicator delivery from diffuse, catchment sources. These investigations suggest a dynamic, but predictable, balance between inputs from the sewerage system and from 'catchment' sources. The sewerage system dominates during low flow conditions but is often overtaken by riverine inputs during high flow conditions after rainfall. Many bathing beach locations exhibit non-compliance after rainfall when stream inputs, rather than sewerage inputs, commonly dominate. The implications of this input pattern is that routine monitoring data may not provide information relevant to new infrastructure planning designed to achieve bathing beach compliance. This suggests that the present scientific information base is insufficient to underpin the extensive UK infra-structure investment programmes designed to ensure compliance with existing EU Directive 76/160/EEC standards. Furthermore, results to date, suggest that management attention must expand from its historical focus on infra-structure provision to incorporate diffuse sources of faecal indicator loading which present a new set of management and modelling challenges.

Biological effects of pollutants in Australian tropical coastal waters: Embryonic malformations and chromosomal aberrations in developing fish eggs

This study establishes baseline information on the biological effects of contaminants in the tropical marine environment of Australia, using as indicators the incidence of embryonic malformation and chromosomal aberration in developing fish eggs. Eighteen sites were examined, including nearshore coastal waters with varying degrees of human activity, and offshore locations on the Great Barrier Reef, in order to assess whether there is any present indication of contaminant effects in the region. Natural background levels of abnormality in embryos and chromosomes of fish are both expected to be less than 10%. All sites examined had chromosomal aberrations well within this limit, and as such, could be classified as uncontaminated by toxicants which have mutagenic effects. Mean rates of embryonic malformation varied with site location, and ranged between 6 and 24%. Coastal sites adjacent to areas used for intensive farming, or with major urban centres, had consistently higher levels of embryo deformity than sites on the Great Barrier Reef. Thus, whilst the incidence of embryonic malformation for the region as a whole (mean 12%) was low in comparison with that of polluted waters (30–80% reported), there is some concern that human activities may be having a localized effect in the region.

Historical changes in age and growth of Atlantic croaker, Micropogonias undulatus (Perciformes: Sciaenidae)

Archaeological excavations near St Augustine, Florida, U.S.A. recovered 415 otoliths from Atlantic croaker, Micropogonias undulatus (Perciformes: Sciaenidae), which were caught by Native American and Hispanic peoples living in the area. Age determination using growth increments of otoliths and correlated size information were used to construct size distributions, age distributions, growth rates and season of capture. During a 3000 year time span, coastal Indians captured Atlantic croaker 1–10 years old ranging from about 13–39 cm total length. Marginal increments of otoliths revealed that most fish were caught from January to May, during or shortly after the period of annulus formation. Numbers and size ranges of otoliths in each archaeological sample were quite small, suggesting that Indian fishing was probably done by individuals or small groups. Gears and methods used by Indians were selective for small, young croaker or were inefficient in areas where large fish occurred. The absence of large, old croaker and nearshore coastal species in Prehispanic collections suggest that Indians fished predominantly in the estuary. Spanish interaction with coastal Indian tribes resulted in changes in the size and age composition of the Atlantic croaker catch. Post-contact, older (up to 15 years) and larger (up to 46 cm, tip of the jaw to the end of the caudal fin—TL) croaker formed a large portion (> 30%) of the catch, suggesting that fishing effort was more extensive throughout estuaries and nearshore coastal waters and may have employed other gears and methods. Marginal increments of otoliths suggest that fishing occurred primarily in winter and spring but may have extended year-round. Comparing information from these collections with modern studies indicates that age and growth of Atlantic croaker have changed dramatically, perhaps in response to exploitation or habitat alteration. In earlier centuries, Atlantic croaker grew more slowly, perhaps an indication of density-dependent growth, and lived much longer (15 years versus 7 years). Differences in age and size class composition of Prehispanic, First Spanish Period, and modern catches are consistent with those of a species whose rates of exploitation have increased. Future research of environmental conditions and the biology of Atlantic croaker and other fishes during these early periods may provide explanations for the dramatic changes in the biology of Atlantic croaker observed in this study.

Evaluation of iron as a triggering factor for red tide blooms

We have examined the relationship between Fe and blooms of the toxic dinoflagellate Alexandrium tamarense (Balech) (formerly Gonyaulax tamarensis var. excavata (Lebour)) using a chemical method that estimates the biological avdability of Fe in seawater. The Fe requirement for optimal growth of A. tamarense in sequential batch culture (ca 3 nM 'available' Fe) was compared with Fe concentrations in waters of the Gulf of Maine, USA. Results indicated that Fe did not limit growth of the organism in nearshore coastal waters or over Georges Bank, but that the organism may have been Fe-limited in Gulf of Maine basin waters. The distribution of A. tamarense in the Gulf of Maine is consistent with these Fe data. Red tide outbreaks in the nearshore environment did not correlate with changes in total Fe or the estimated Fe availability. Although Fe did not appear to trigger outbreaks of A. tamarense in Maine coastal waters, the findings are consistent with suggestions that pulsed inputs of Fe may be important for the development of toxic dinoflagellate blooms in regions (e.g. Florida) where outbreaks are initiated offshore.

Time Series Analyses of Suspended Sediment Concentrations at North Inlet, South Carolina

Daily water samples have been collected at three stations in the North Inlet (South Carolina) marshestuary system since February 1981 as part of the NSF Long-Term Ecological Research (LTER) project. As a result of this sampling regime, nearly continuous time series of inorganic and organic suspended sediment, particulate organic carbon (POC), Secchi disk, salinity, and water temperature are now available. Power spectrum analysis of these data reveals that most of the explainable variance in the inorganic suspended sediment, POC, and Secchi disk data is related to a yearly cycle that is strongly coherent with water temperature such that high turbidity is associated with high water temperature. Only a small fraction of the explainable variance is associated with frequencies that can be related to the semidiurnal tide. Simple correlation analysis also indicates that turbidity is more closely associated with water temperature than with tide height or salinity. The ratio of POC to inorganic suspended sediment shows no discernible power spectra peaks and is weakly, but inversely, correlated with temperature. From these results we hypothesize that temperature-regulated bioturbation is the main factor controlling turbidity variations in the system. The lack of a strong inverse correlation between turbidity and salinity suggests that river runoff has little immediate impact on the suspended sediment of nearshore coastal waters in systems similar to North Inlet.

The EC Bathing Water Directive: a Sampling Problem

AbstractThe relatively frequent observation, during periods of onshore drift, of a surface line of convergence in nearshore coastal waters may have significant implications for the sampling procedure used for monitoring compliance with the EC Bathing Water Directive. A simple theory is developed for predicting the formation of the convergence line, and a possible alternative sampling method is suggested.

Dispersion of Sewage Wastes in Nearshore Coastal Waters: Applicability of Water Quality Criteria

Deepwater outfalls can be satisfactorily designed to ensure rapid dilution of sewage wastes, and allow for conventional water quality criteria which prescribe low bacterial levels in areas used for recreational purposes and shellfish harvesting, to be achieved. However, surface shoreline discharges of similar wastes dissipate far less readily, and normally result in shoreline bacterial levels far in excess of desirable criteria. The absolute assessment of water quality in suspect areas should ideally also include viral counts as well as epidemiological information on infections of persons exposed to contaminated seawater or seafood.

228Ra/ 226Ra ratios in coastal waters of Kalpakkam

Studies of 226Ra and 228Ra concentrations in ocean waters provide a means of estimating ocean mixing rates, as has been demonstrated by a number of investigators. In this context, there is a considerable paucity of such data in coastal waters, whose radium concentrations are expected to vary significantly, relative to oceanic waters, due to terrigenous influences. The present study was carried out in the nearshore coastal waters of Kalpakkam (12° 33′N, 80° 11′E), which is the site of a major nuclear complex in Southern India. The results of this study show that dissolved 226Ra and 228Ra concentrations in nearshore seawaters range from 1·06 to 2·64 mBq litre −1 (mean 1·75 mBq litre −1) and from 4·15 to 7·8 mBq litre −1 (mean 5·94 mBq litre −1) respectively, with 228Ra/ 226Ra activity ratios of 2·3 to 4·9 (mean 3·4). However, the backwaters tend to show somewhat elevated dissolved 226Ra and 228Ra levels, ranging from 1·8 to 5·7 mBq litre −1 (mean 3·56 mBq litre −1) and from 14·3 to 71·7 mBq litre −1 (mean 44·6 mBq litre −1 respectively, with radium activity ratios from 7·9 to 15·3 (mean 12·5). This paper presents the results of a comprehensive study aimed at investigating 226Ra and 228Ra associated with the dissolved and particulate phases in the nearshore marine environment of Kalpakkam. Our earlier studies at the site have shown the presence in the area of the mineral monazite and this could be of significance in generating the observed high 228Ra/ 226Ra ratios in the dissolved and particulate phases along the Kalpakkam coast.

Survival of Candida albicans in tropical marine and fresh waters.

A survey of Candida albicans indicated that the organism was present at all sites sampled in a rain forest stream and in near-shore coastal waters of Puerto Rico. In the rain forest watershed no relationship existed between densities of fecal coliforms and densities of C. albicans. At two pristine sites in the rain forest watershed both C. albicans and Escherichia coli survived in diffusion chambers for extended periods of time. In near-shore coastal waters C. albicans and E. coli survival times in diffusion chambers were enhanced by effluent from a rum distillery. The rum distillery effluent had a greater effect on E. coli than on C. albicans survival in the diffusion chambers. These studies show that neither E. coli nor C. albicans organisms are good indicators of recent fecal contamination in tropical waters. It further demonstrates that pristine freshwater environments and marine waters receiving organic loading in the tropics can support densities of C. albicans which may be a health hazard.

Morphological and behavioral antipredatory adaptations of decapod zoeae.

Zoeae of some species of estuarine decapods are retained in the estuary throughout development while others are exported into nearshore coastal waters. The horizontal migrations of decapod zoeae to coastal waters may have evolved to reduce the probability of encountering planktivorous fishes which are most abundant in the estuary. If so, then the morphological vulnerability of zoeae to fish predation should be inversely related to the number of predators occurring where they develop. Six species of estuarine decapod zoeae were offered to Menidia menidia and Fundulus heteroclitus. The behavioral interactions were observed to determine the prey's vulnerability to predation, and the mode of operation and relative effectiveness of their defenses. Feeding trials and behavioral observations both demonstrated that M. menidia 6-16 mm long preferred Uca minax and Callinectes sapidus zoeae, which are exported from the estuary, to Rhithropanopeus harrisii, Sesarma reticulatum and Palaemonetes pugio, which are retained within estuaries. Pinnotheres ostreum zoeae develop in the lower estuary and fish demonstrated an intermediate preference for the zoeae. Menidia menidia 20-40 mm long showed similar preferences for R. harrisii S. reticulatum, P. ostreum and U. minax as did small silversides. Large-mouthed demersal fish, Fundulus heteroclitus 6-10 mm long, also preferred U. minax to R. harrisii, but more readily preyed on zoeae than did M. menidia. The exported species of zoeae have shorter spines and smaller bodies than do retained zoeae, except P. ostreum which is small, spineless and passively sinks when attacked by fish. Other retained species of zoeae also have postcontact behavioral defenses which enhance the effectiveness of their morphological defenses. Zoeae do not evade attacks by fishes, but fishes quickly learned to avoid zoeae, which increases the effectiveness of the zoeae's antipredatory adaptations.

Survival and distribution of aeromonas hydrophila in near-shore coastal waters of Puerto Rico receiving rum distillery effluent

For a period of 1 year, monthly water samples were taken for estimates of Aeromonas hydrophila density at 6 sites in Ensenada de Boca Vieja near San Juan, Puerto Rico. Five sites were associated with the effluent plume of the world's largest rum distillery, the sixth site was 177 m upcurrent. Fifteen water quality parameters were monitored concurrently with A. hydrophila estimates. The toxic and stimulatory nature of the effluent made correlations with any physicochemical parameter difficult. However, a significant multiple regression was obtained against density of A. hydrophila using temperature, total phosphorus, total organic carbon and orthophosphates. Densities of A. hydrophila were always higher in the effluent plume and usually highest at the site closest to effluent outfall. Suspensions of A. hydrophila placed in diffusion chambers at the effluent point source not only survived, but gradually increased in density, while 500 m upcurrent densities of A. hydrophila in diffusion chambers rapidly declined. Significant differences in A. hydrophila density between the two sites could be detected after only 18 h. The diffusion chamber studies confirm natural correlations with water quality that indicate A. hydrophila densities in marine habitats can become elevated under the appropriate conditions. Higher densities of other potential pathogens e.g. Klebsiella pneumoniae, Vibrio cholerae, were also observed in the rum distillery effluent plume.

Structure and chemistry of sediments in Belfast Lough, a semi-enclosed marine bay

In a study of the benthic environment of Belfast Lough the structure of the subtidal sediment was examined along with its content of organic matter and selected metals (Cr, Mn, Ni, Cu, Zn, Pb). A wide range of sediment types occurred within the lough but the mean grain sizes for individual sites lay predominantly within the size classes of fine sand, very fine sand and silt. The content of organic matter and metals in the sediments showed strong positive correlations with each other and with the content of silt/clay. Both organic matter and metals decreased in concentration in a seawards direction. The content of organic matter lay generally within the range of 1–5% which is normally associated with shelf sediments, but constituted up to 12% of the sediment in the docks area. Likewise, metals were usually within the range reported within other nearshore coastal waters of the U.K., but sediments in the docks area and inner lough were enriched with several metals. Cluster analysis identified four major subdivisions in the lough which were distinctly different in their contents of silt/clay, organic matter and metals.

CONSECUTIVE HIGH WAVES IN COASTAL WATERS

The problem of statistics of numbers of consecutive high waves has not yet been treated in detail. Some numerical results (Goda, 1970) and evaluations of prototype data in water depths of 100 m (Rye, 1975) and 40 m (Wilson and Baird, 1973) respectively were published. Data from measurements in nearshore coastal waters, with unbroken, breaking and broken waves, obtained in the Elbe estuary, are treated in this paper.

Water Quality and Effluent Standards of Hawaii

The sequential development of water quality standards for the State of Hawaii, commencing with the passage of the federal Water Quality Act of 1965, resulted in the enactment of receiving water standards in January 1968 that were expressed in terms of basic freedoms and through eight specific standards which applied to separate classes (two fresh waters and three coastal waters) of all surface fresh and near and offshore coastal waters in the state. In order to meet the receiving water requirements at the point of discharge the present or potential discharger can apply for a variance or zone of mixing permit within specific boundaries. The enactment of PL 92-500 together with other reasons prompted the state to develop effluent limitation standards (effective August 1973) that apply to fresh and nearshore coastal waters and subsurface discharges which for practical reasons are limited to discharges of less than 1 mgd (3,785 m³/day) that have received tertiary treatment.