Estuarine Embayment Research Articles

Nutrient release and sediment oxygen demand in a eutrophic land-locked embayment in Hong Kong

Tolo Harbour is a large eutrophic land-locked estuarine embayment in Hong Kong. The rapid urbanization, commercio-industrial activities and lack of legislative control around the Tolo catchment produced large quantities of untreated or partially treated municipal sewage, agricultural wastes and cottage industrial effluents which were discharged into Tolo Harbour via rivers and watercourses. Control measures were implemented to reduce the external nutrient loading into the harbour since the early 1980s. Nutrient data for the period 1982 to 1997 were analyzed for temporal trends. Over the period of observation, the total inorganic nitrogen and total phosphorus both show an increasing trend, despite a decade of efforts in reducing nutrient loading. The release rates of potentially mobile nitrogen (N) and phosphorus (P) from the sediments collected from Tolo Harbour were determined by N and P release experiments under oxic conditions. The experimental results showed that the sediment released significant amount of nutrients, especially orthophosphates and ammonia nitrogen. The maximum release rates were 15.0 and 206.0 mg/m 2/day, respectively. Although the external nutrient loading has been reduced, nutrients could gradually be released back into the water column from the contaminated sediments and delay improvement of the water quality.

Geochemistry and particle size of surface sediments of Exmouth Gulf, Northwest Shelf, Australia

Exmouth Gulf is a shallow (mean depth 11.9 m, 2600 km 2 area) inverse estuarine embayment on the northwest shelf of Australia, with a catchment area of 6400 km 2 with low human and livestock populations in an arid climate. The Gulf is an extreme example of a tide and wave dominated estuary, with very small river inputs. Freshwater supply from the land is very small, and terrestrial run-off nutrient supply is estimated to be 0.8 mmol TN and 0.4 mmol TP per square metre Gulf area per year (TN=total dissolved and particulate nitrogen, TP=total dissolved and particulate phosphorus). Holocene deposits in the mangrove margins are less than 1 m thick, and are relict and partly aeolian in origin. Surficial sediments are largely quartz and calcite sand, and fine-grained recent sediments are probably removed by energetic Indian Ocean tide and wave mixing and circulation. Geochemical variations in sediment composition across the Gulf are small, and appear to be little affected by redox cycles. Marine organic matter is efficiently decomposed, leaving behind excess phosphorus associated with carbonate and iron-rich sediments. The thin ribbon of stunted mangroves along the eastern margin of the Gulf has little influence on the composition of sedimentary organic matter in the Gulf, and the mangrove sediments are not a trap for trace elements as has been found in other parts of the tropical world. Ba, Li, Pb, and Cu vary in direct proportion to the abundance of the bulk sediment aluminosilicate fraction, boron is enriched by evaporation in the supratidal saltflat regions, and cadmium has large variations perhaps related to the carbonate fraction of the sediments. There is little evidence for coastal trapping of sediment and oceanic elements in Exmouth Gulf, and some regions of the intertidal mangrove and saltflat zones are being eroded into the Gulf and adjacent shelf.

LEPIDOPHTHALMUS MANNINGI, A NEW GHOST SHRIMP FROM THE SOUTHWESTERN GULF OF MEXICO (DECAPODA: THALASSINIDEA: CALLIANASSIDAE)

Lepidophthalmus manningi, new species, is described from intertidal and shallow subtidal margins of estuarine embayments, ephemeral tidal ponds, and river mouths in the states of Veracruz, Tabasco, and Campeche, eastern Mexico. This apparent endemic of the southwestern Gulf of Mexico is ornamented by conspicuous sclerotized plates on ventral surfaces of the abdomen, a feature it shares with several other tropically distributed species in the western Atlantic and eastern Pacific. Lepidophthalmus manningi is very close in morphology to the recently described L. richardi from Belize, its apparent sibling, but can be distinguished by unique features in sculpture and shape of not only the ventral abdominal plating, but also in structures such as the eye tubercles, major chelipeds, and the anterior two pleopod pairs, dorsal abdominal tergites, and the uropods. It is readily distinguishable from two other Gulf of Mexico species, both of which lack ventral sclerotized plates on the abdomen. The latter include the widely distributed warm-temperate species, L. louisianensis, which ranges throughout the northern Gulf of Mexico and into Tamaulipas, Mexico, and a second southwestern Gulf endemic form that remains undescribed and is currently under study. Disjuncture of appropriate habitats in the northern Yucatan Peninsula and limited dispersal ability in the genus appear to account for isolation of L. manningi from its Caribbean sibling.

Meiofaunal Colonization of Artificial Substrates in an Estuarine Embayment

Abstract. Artificial substrates were used to investigate the cryptic meiofauna of a Louisiana estuary. Three types of collectors were used as artificial habitats in colonization studies. Mesh collectors (composed of a plastic thread, approximately 74 m long, woven into a pad) and bottle brushes (with approximately 4400 plastic bristles per brush, each 2.5 mm long) were colonized equally well by meiofauna; Hester‐Dendy plates with less structural complexity were colonized at a slower rate, especially by copepods. Nematodes and harpacticoid copepods were always the two most abundant meiofaunal taxa collected. Mesh collectors were retrieved in July and December after a 2‐week colonization period to examine seasonal trends. Starting in December, a long‐term colonization study was also performed to determine if an equilibrium abundance could be achieved; artificial substrates were collected after 2, 4 and 8 weeks. Meiofauna achieved high abundances (means ranged from 1000 – 20,000 individuals per collector) on artificial substrates regardless of season, and abundance was related to supply, water flow and capture efficiency of the substrates as well as behavior of the meiofauna. Copepod species diversity was low (6 species were observed in July and 11 in December). Diversity and evenness were significantly different between July and December, and among the three collections in the long‐term study. The copepod species assemblage qualitatively differed between July and December. Our data suggest that an abundant and dynamic but understudied meiofaunal assemblage is present in this estuarine embayment. This assemblage is not associated with macroalgae but rather related to presence of hard substrates and seasonally abundant filamentous microalgae.

Variations in sedimentary environments and accretionary patterns in estuarine marshes undergoing rapid submergence, Chesapeake Bay

Major processes controlling sedimentological characteristics and accretionary rates and patterns were evaluated in two of the most common tidal marsh settings (estuarine tributaries and estuarine embayments) in Chesapeake Bay, one of the largest microtidal estuaries in the world. Textural analyses of 29 vibracores show spatial and temporal trends in grain size and organic matter which reflect differences in depositional settings within the marshes and changes in the controlling processes, as well as broader events in the surrounding watersheds. Spatially, the surficial sediments normally follow expected patterns, with coarsest sediments and lowest organic matter contents found in bay margin or channel margin locations, while the finest, organic-rich sediments occur in interior and submerged upland marshes. However, temporally, the marshes do not always show the expected increasing dominance of organic input over time (indicated by increasing % loss on ignition with decreasing depth), indicative of the marsh building process. Sea-level rise, tidal channel migrations, and anthropogenic effects likely contribute to decreases in organic matter contents in the upper sediment column. Furthermore, accretion rates and stratigraphic characteristics can be affected by these same processes, illustrating the importance of understanding temporal changes in marsh depositional environments over various time scales before sedimentologic and accretionary patterns are evaluated. Examination of the vibracores reveals that the marsh is composed of a complex stratigraphy with at least four major stratigraphic sequences occurring: (1) emerging or developing marsh sequences characteristic of channel margin and interior marshes; (2) submerging or mineral matter enriched marshes, also characteristic of channel and interior marsh areas; (3) high-energy marsh sequences characteristic of bay margin environments; and (4) submerged upland marsh sequences. The sedimentological properties of the stratigraphic sequences are controlled by overwash processes, tidal channel migrations, duration of tidal flooding, various anthropogenic effects, and sea-level rise. Accretion rates and patterns over the last ∼200 years, determined from pollen histories, differ between the marshes along the estuarine tributary (Nanticoke River) and those found in the tidal embayment (Monie Bay). Marshes in the upper-estuarine tributary have a larger riverine sediment input, and trapping of the high sediment loads in the upper estuary often yields marsh accretion rates (maximum of 0.74 cm/yr) which are greater than relative sea-level rise (∼0.4 cm/yr), resulting in stable marshes. By comparison, estuarine processes limit penetration of high sediment loads to the lower reaches of marshes along the tributary and, as a consequence, accretion rates are generally lower than the rate of relative sea-level rise, and marsh loss is prevalent. Overall, accretion rates in the marshes in the embayment are close to or less than the local sea-level rise and do not have as distinctive spatial patterns as the tributary marshes. Although marsh loss has yet to be identified as a significant process here, decreases in organic content of the upper sediment column may signal the early stages of submergence due to sea-level rise.

Sediment Oxygen Demand and Nutrient Release in An Eutrophic Estuarine Embayment in Hong Kong

Sediment Oxygen Demand and Nutrient Release in An Eutrophic Estuarine Embayment in Hong Kong

Water quality and phytoplankton dynamics in Moreton Bay, south-eastern Queensland. I. Field survey and satellite data

The water quality of Moreton Bay, a sub-tropical estuarine embayment in south-eastern Queensland, was monitored over a 2-year period. Surveys in situ and ground-truthed satellite imagery were used to describe the temporal and spatial variability in water-quality indicators and the level of eutrophication. Strong east–west gradients in chlorophyll α and water clarity were found. During the study period fluvial discharges, which all enter on the western littoral, were below their long-term averages, and nutrient loading to the bay was dominated by point-source wastewater discharges along the western boundary. The data suggest that although the impact of nutrient loads on the bay’s eastern side is mitigated by tidal intrusion of oceanic water, the western areas are already degraded and can be considered mesotrophic to eutrophic. This part of the bay may deteriorate further with the projected future population expansion in the bay’s catchment.

Transgressive systems tract development and incised-valley fills within a Quaternary estuary-shelf system: Virginia inner shelf, USA

High-frequency Quaternary glacioeustasy resulted in the incision of six moderate-to high-relief fluvial erosion surfaces beneath the Virginia inner shelf and coastal zone along the updip edges of the Atlantic continental margin. Fluvial valleys up to 5 km wide, with up to 37 m of relief and thalweg depths of up to 72 m below modern mean sea level, cut through underlying Pleistocene and Mio-Pliocene strata in response to drops in baselevel on the order of 100 m. Fluvially incised valleys were significantly modified during subsequent marine transgressions as fluvial drainage basins evolved into estuarine embayments (ancestral generations of the Chesapeake Bay). Complex incised-valley fill successions are bounded by, or contain, up to four stacked erosional surfaces (basal fluvial erosion surface, bay ravinement, tidal ravinement, and ebb-flood channel-base diastem) in vertical succession. These surfaces, combined with the transgressive oceanic ravinement that generally caps incised-valley fills, control the lateral and vertical development of intervening seismic facies (depositional systems). Transgressive stratigraphy characterizes the Quaternary section beneath the Virginia inner shelf where six depositional sequences (Sequences I–VI) are identified. Depositional sequences consist primarily of estuarine depositional systems (subjacent to the transgressive oceanic ravinement) and shoreface-shelf depositional systems; highstand systems tract coastal systems are thinly developed. The Quaternary section can be broadly subdivided into two parts. The upper part contains sequences consisting predominantly of inner shelf facies, whereas sequences in the lower part of the section consist predominantly of estuarine facies. Three styles of sequence preservation are identified. Style 1, represented by Sequences VI and V, is characterized by large estuarine systems (ancestral generations of the Chesapeake Bay) that are up to 40 m thick, have hemicylindrical wedge geometries, and occur within large, coast-oblique trending depressions (paleo-estuaries). Style 1 is dominated by fluvial through estuary-mouth depositional systems (Seismic Facies 1–4). Style 2 sequence preservation, represented by Sequences III and II, is dominantly an inner shelf and shoreface succession with a seaward-thickening tabular wedge geometry that does not exceed 15 m in thickness. These shoreface and inner shelf depositional systems of the upper transgressive systems tract (Seismic Facies 9) and highstand systems tract (Seismic Facies 7 and 11) are not associated with paleo-estuaries. Style 3 sequence preservation is represented by Sequence I, the Holocene Sequence. It consists of lower transgressive systems tract fluvial-estuarine, lagoonal, and tidal-inlet fill deposits (Seismic Facies 1–6, and 8) overlain by upper transgressive systems tract shelf and shoreface sands (Seismic Facies 9). Style 3 has a crenulated wedge geometry, and is thickest beneath and seaward of the modern Chesapeake Bay mouth. It thins northward and landward onto Late Pleistocene interfluvial highs on the basinward side of the southern Delmarva Peninsula.

Patterns of late Palaeozoic deglaciation in the Paraná Basin, Brazil

Abstract The Itarare Subgroup (Middle Carboniferous-Early Permian) of the Parana Basin of southeastern Brazil contains the thickest, most extensive and one of the longest records of late Palaeozoic glaciation in all of the Gondwana supercontinent. Glacially controlled deposition started as early as the Middle Carboniferous when lobate termini of ice streams from the Windhoek Ice Sheet (WIS), and Rio Grande do Sul and Asuncion ice caps moved into the Parana Basin. Lobes reached sea-level and advanced grounded at least as far as 200 km into the basin, stabilizing as tidal/intertidal margins. Glaciation and glacial sedimentation occurred penecontemporaneously with the transgressive phase of the late Palaeozoic tectonic cycle of the Parana Basin, while Gondwana was gradually moving away from the South Pole. Evolution involved complex interaction of tectonic, palaeogeographic and palaeoclimatic factors. Initial flooding of the basin by an epicontinental sea in the Middle Carboniferous may have provided moisture necessary for the growth of glaciers. Conversely, episodes of sea-level rise probably affected the stability of marine glaciers. The palaeoclimatic setting for the WIS and other ice masses at the margins of the Parana Basin was mostly temperate. Multiple ice advances are evidenced by subglacial tillites resting on striated and/or glaciotectonized basement and deformed glacigenic sediments identified at different stratigraphic levels in the Itarare Subgroup. Glaciation reached its maximum expansion sometime between the Late Carboniferous and Early Permian, gradually diminishing and vanishing in the late Early Permian. The reconstructed palaeogeographic evolution favors a model of irregular melt back of ice masses, particularly along the eastern margin of the Parana Basin, in analogy with the deglacial pattern of the Pleistocene Laurentide ice sheet, in North America. Retreat of marine glaciers was mostly associated with relatively simple accumulations, or complex build-ups of ice contact/proglacial facies associations in glacial estuarine embayments. Fast retreat was mainly controlled by decoupling associated with sea-level rise and intense calving. In the terrestrial environment, more fragmentary evidence shows that retreat may have involved several mechanisms including downwasting of stagnant/inactive ice margins and destabilization by surging of glaciers moving over deformable sediments. Highstand sea-level following ice wastage is often marked by widespread deposition of relatively thin marine beds. At least four stratigraphically different basinwide marine “horizons” are recognized. Isostatic rebound of deglaciated margins of the Parana Basin is recorded by transition from deep marine beds to shallowing/coarsening upward, prograding sequences of littoral/fluvio-deltaic facies basinwards, sourced from raised basin margins. Eventually, upon emersion, these constituted platforms for interglacial and postglacial peat development. Although glaciation lasted for a long time, glacial sedimentation alternated with relatively long periods of intense and widespread subaerial and subaquatic (submarine) reworking of previously deposited glacigenic sediments and deposition of “normal”, non-glacial sediments, that comprise the bulk of the Itarare Subgroup sequence. Thin coal beds, which locally rest on fossil soils, denote climatic amelioration during these interglacial phases.

Ichthyoplankton Assemblage Structure in Mississippi Sound as Revealed by Canonical Correspondence Analysis

The spatiotemporal dynamics of the ichthyoplankton assemblage structure were investigated in Mississippi Sound, a northern Gulf of Mexico estuary. The study was based on a comprehensive survey constituting 528 collections from 22 stations over 12 months at two tow depths. Important environmental correlates of assemblage structure were identified using canonical correspondence analysis (CCA). A wide taxonomic diversity was encountered during the ichthyoplankton survey, including 152 taxa distributed among 48 families. Strong physical gradients in water temperature, dissolved oxygen and salinity correlated predominantly with ichthyoplankton assemblage structure, and reflected substantial spatiotemporal variation. The CCA results were interpreted in light of adult life-style characteristics. Ecological groups of larvae, as defined by adult life-style characteristics for respective taxa, showed distinctive dispersion patterns in 2-dimensional canonical space. A diverse group of offshore demersal taxa clustered as larvae in a region of CCA space corresponding spatiotemporally with stations located in passes and outside of the Sound during late summer and autumn. Other ecological groups, such as the inshore nektonic and offshore pelagic fishes, were widely dispersed as larvae in canonical space, with member taxa occurring under dissimilar physical conditions. Estuarine embayments in the north-central Gulf of Mexico, like Mississippi Sound, might be viewed appropriately as landwardmost sections of the wider, highly productive nursery grounds of this region.

Three-layered circulation in reverse estuaries

Driven by an upper-layer density deficit and lower-layer density surplus from an adjacent sea, circulation in an estuarine embayment may be three-layered, with top and bottom inflows separated by a mid-layer outflow. The characteristics of this type of circulation as functions of density forcing, background stratification and lateral depth variation in an embayment are examined using a three-dimensional primitive-equation model with a free surface. Among all the details, the dominance of bottom intrusion over the surface one stands out and presents a departure from early models that have missed the importance of bottom intrusion in regulating the three-layered layered circulation. A strong or deeper upper density deficit from the adjacent sea, bottom stress and narrowing estuary width at depths all produce transients discouraging the development of the bottom intrusion. In time, the bottom inflow invariably gains strength and thickness and squeezes up the core of the mid-layer outflow to above the mid-depth. A heuristic argument follows to explain this counter-intuitive result.

A water quality management model for the Lakes Bay estuarine embayment 2: Hydrodynamic tidal model

Abstract A time variable tidal flow model was developed to be used interactively with a two‐dimensional, finite segment, water quality model. The continuity equation and the equation of motion were used as coupled model equations and formulated in a finite segment format. Numerical solutions were obtained using a two ‐ step explicit method where velocities, tidal heights, and segment volume were adjusted at half‐time intervals. The model calibration/verification was based on recorded tidal elevation data. The model predictions are in close agreement with the measured data.

A water quality management model for the Lakes Bay estuarine embayment 1: Receiving water quality model

Abstract Mathematical models were constructed to estimate the non‐point pollutant loadings from an urbanizing area as well as to model the assimilative capacity of the receiving tidal embayment system. The models are capable of simulating the hydrologic aspects as well as the water quality cycles of the system as a function of urbanization. In determining the response of the receiving water system to stormwater loadings, the change in receiving water quality is modeled spatially as well as temporally. The overall model is composed of three subsystem models: a stormwater model, a hydrodynamic tidal model, and a receiving water quality model. Construction of the stormwater model is based on STORM (Storage, Treatment, Overflow, Runoff Model) by the U.S. Army Corps of Engineers. A ground water component to the model was added to adjust the model for application to the study area, Lakes Bay, New Jersey. The receiving water quality model is a two‐dimensional time variable water quality model which is based on a...

Peat-accumulating depositional systems of Sarawak, East Malaysia

Many coal deposits originate in deltaic, estuarine, and coastal plain settings and a knowledge of interrelationships between the tectonic and depositional elements active at the time of sediment deposition is necessary to formulate basin scale models. The prograding coastal depositional systems of Sarawak all contain domed peat-accumulating environments in which low-ash, low-sulfur peats are being deposited in areas of active clastic siliciclastic sedimentation. These depositional systems are as large as 11,400 km 2 and individual peat deposits within systems are in excess of 20 m thick and 1000 km 2 in area. The geographic positions and drainage basin areas of each depositional system are controlled by fault and fold systems. Although prograding into the same receiving basin, individual system geomorphology is variable and ranges from a wave-dominated microtidal delta, to a wave-dominated meso- to macro-tidal delta/coastal plain system, to a tide-dominated macrotidal estuarine embayment along a 450 km stretch of coastline. System variation is a function of sediment supply, shelf and embayment geometry, wave climate, and tidal range. These factors, which control depositional system geomorphology, also control the resulting long axis orientation of the thick, domed peat deposits. The surface vegetation and internal characteristics of most domed peat deposits, however, are similar. Internal characteristics consist of basal high-ash, high-sulfur, degraded peats overlain by low-ash, low-sulfur, well preserved peats in vertical profile. These systems demonstrate variable responses to late Pleistocene/Holocene sea-level rise and, in these instances, the variation is most attributable to local differences in siliciclastic sediment supply, which is a function of the drainage basin area.

Nutrient Flux in a Landscape: Effects of Coastal Land Use and Terrestrial Community Mosaic on Nutrient Transport to Coastal Waters

Long-term interdisciplinary studies of the Rhode River estuary and its watershed in the mid-Atlantic coastal plain of North America have measured fluxes of nitrogen and phosphorus fractions through the hydrologically-linked ecosystems of this landscape. These ecosystems are upland forest, cropland, and pasture; streamside riparian forests; floodplain swamps; tidal brackish marshes and mudflats; and an estuarine embayment. Croplands discharged far more nitrogen per hectare in runoff than did forests and pastures. However, riparian deciduous hardwood forest bordering the cropland removed over 80 percent of the nitrate and total phosphorus in overland flows and about 85 percent of the nitrate in shallow groundwater drainage from cropland. Nevertheless, nutrient discharges from riparian forests downslope from croplands still exceeded discharges from pastures and other forests. The atomic ratio of nitrogen to phosphorus discharged from the watersheds into the estuary was about 9 for total nutrients and 6 for inorganic nutrient fractions. Such a low N:P ratio would promote nitrogen rather than phosphorus limitation of phytoplankton growth in the estuary. Estuarine tidal marshes trapped particulate nutrients and released dissolved nutrients. Subtidal mudflats in the upper estuary trapped particulate P, released dissolved phosphate, and consumed nitrate. This resulted in a decrease in the ratio of dissolved inorganic N:P in the estuary. However, the upper estuary was a major sink for total phosphorus due to sediment accretion in the subtidal area. Bulk precipitation accounted for 31 percent of the total nongaseous nitrogen influx to the landscape, while farming accounted for 69 percent. Forty-six percent of the total non-gaseous nitrogen influx was removed as farm products, 53 percent either accumulated in the watershed or was lost in gaseous forms, and 1 percent entered the Rhode River. Of the total phosphorus influx to the landscape, 7 percent was from bulk precipitation and 93 percent was from farming. Forty-five percent of the total phosphorus influx was removed as farm products, 48 percent accumulated in the watershed, and 7 percent entered the Rhode River. These nitrogen and phosphorus discharges into the Rhode River, although a small fraction of total loadings to the watershed, were large enough to cause seriously overenriched conditions in the upper estuary.

Geoarchaeology of Johns Bay, Maine

AbstractThis study examines the Holocene history of a glacially‐sculpted Maine embayment using both geological and archaeological data bases. High‐resolution seismic profiling, in combination with vibracores and Holocene sea‐level curves, were used to develop the Holocene stratigraphy and paleogeographic evolution of Johns Bay and Pemaquid Beach, Maine. These geological databases were, whenever possible, integrated with the Johns Bay archaeological database and general archaeological settlement paradigms for coastal Maine. As sea level has risen from its ‐65 m lowstand at the beginning of the Holocene, Johns Bay has evolved from a narrow fluvial system, to an estuary, to its present form of an open embayment. Over roughly the last 4000 years, the Pemaquid Beach area has changed from a forested upland, to a bedrock‐pinned freshwater wetland, to a pocket barrier fronting a small salt marsh. The barrier continues to migrate over the salt marsh, which is transgressing the freshwater environments. The first evidence of human settlement in Johns Bay is at 4000–5000 yr B.P. Archaeological site distribution around Johns Bay has been examined in light of an estuarine embayment evolution model developed for the Maine coast. Sites are concentrated in zone 1 (the inner embayment). This zone is currently experiencing sediment accumulation. Zone 2 (middle embayment) is undergoing erosion, and zone 3 (outer embayment) has been stripped of sediment. Archaeological sites in these outer areas have been eroded. The Pemaquid Beach area has a history of occupation dating back 4000–5000 years. The last 2000 years of this record is found in stratigraphic context in the Nahanada site. The first 3000 years is represented by a collection of artifacts found out of context on the beach in front of the Nahanada site. The artifacts, dated by morphology, present a time continuum from 4000–5000 yr B.P. until the occupation of the Nahanada site. Thus, it is suggested that the Nahanada site represents the back of a chronologically shingeled settlement area that extended to the 5000 yr B.P. shoreline. Finally, a model for the development of chronologically shingled sites is suggested.

Traps Associated with Paleovalleys and Interfluves in an Unconformity Bounded Sequence: Lower Cretaceous Glauconitic Member, Southern Alberta, Canada (1)

The Glauconitic member in Badger, Little Bow, Retlaw, and Turin fields is an unconformity bounded sequence that formed on an ancient coastal plain in response to relative sea level fluctuations. The member consists of valley-fill and inter-valley strata. Valley-fill sandstone bodies are thick elongate pods that formed from inner estuarine bars when sedimentation was laterally confined between valley margins. Inter-valley sandstone bodies are thin discontinuous sheets that accumulated during highstands when outer estuarine embayments covered interfluvial areas adjacent to associated valleys. Numerous oil pools are stratigraphically trapped within quartzose sandstones in valley-fill and inter-valley strata of the Glauconitic member in the study area. Common updip seals for these reservoirs are (1) intra-sequence facies changes from sandstone to shale, and (2) low-permeability lithic sandstones that fill the cross-cutting paleovalleys of a younger sequence. Traps associated with many valley-fill pools are enhanced by differential-compaction anticlines. Several oil pools in the study area are hosted by discrete quartzose sandstone bodies that lie beneath a valley filled with low-permeability lithic sandstone. These quartzose sandstone bodies are interpreted to be remnants of older Glauconitic deposits that escaped erosion when a younger valley incised into, and followed the trend of, one or more older Glauconitic valleys.

Runoff-induced metals in Lakes Bay, New Jersey

Lakes Bay, an estuarine embayment located near Atlantic City, New Jersey, currently supports commercial shellfishing; however, the surrounding basin is a prime location for development. Synpotic surveys were conducted during the summer of 1986 to determine background conditions and the response to stormwater runoff inputs of three metals; copper, lead and cadmium. Background (dry weather) conditions of all three metals were found to be not significantly different than those reported for world natural waters. Significant amounts of lead and copper were found to be input to the system through a major storm water sewer that discharges to a lagoon. Sediment analysis showed that considerable sedimentation occurs in this lagoon, thus localizing the effect of this input to the system. A local stormwater retention basin was not found to be a significant source of metals. Cadmium levels were not found to be significantly different between dry and wet weather conditions. The high salinity of the system required extensive sample extraction procedures prior to analysis by atomic absorption spectrophotometry to minimize matrix interferences.

RUNOFF-INDUCED METALS IN LAKES BAY, NEW JERSEY

Lakes Bay, an estuarine embayment located near Atlantic City, New Jersey, currently supports commercial shellfishing; however, the surrounding basin is a prime location for development. Synpotic surveys were conducted during the summer of 1986 to determine background conditions and the response to stormwater runoff inputs of three metals; copper, lead and cadmium. Background (dry weather) conditions of all three metals were found to be not significantly different than those reported for world natural waters. Significant amounts of lead and copper were found to be input to the system through a major storm water sewer that discharges to a lagoon. Sediment analysis showed that considerable sedimentation occurs in this lagoon, thus localizing the effect of this input to the system. A local stormwater retention basin was not found to be a significant source of metals. Cadmium levels were not found to be significantly different between dry and wet weather conditions. The high salinity of the system required extensive sample extraction procedures prior to analysis by atomic absorption spectrophotometry to minimize matrix interferences.

RELATIVE GROWTH AND SEXUAL MATURATION IN THE ESTUARINE GHOST SHRIMP CALLIANASSA LOUISIANENSIS SCHMITT, 1935

In Callianassa louisianensis, ovarian development becomes evident in December and con­ tinues through the spring. Ovigerous females occur primarily from early June through August, less frequently into September. Recruitment occurs throughout the summer and early fall, and juveniles reach large enough size to be detected in our samples by early spring. First-year females enter the breeding population the following summer; the smallest ovigerous among these have attained a carapace length (CL) of almost 11 mm. Analysis of relative growth suggests that females enter a maturation growth phase at about 11 mm CL, while males enter a maturation phase at near 15.5 mm CL. In males, this transition is marked by a strong increase in the relative growth of the major chela, together with a change in shape of the chela. In females, there is a decrease in the relative growth of the major chela after maturation. Carapace lengths in females do not attain the size of those in the largest males. In the maturation phase, female growth appears directed toward lengthening of the abdomen and development of ovaries, while in males it is directed toward development of the major chela, a secondary sexual structure that may be utilized in aggressive encounters. The ghost shrimp Callianassa louisianen­ sis (treated formerly as Callianassa jamaicense var. louisianensis Schmitt, 1935) is a widespread and abundant component of the estuarine macroinvertebrate assemblage in the northern Gulf of Mexico (Willis, 1942; Hedgpeth, 1950; Wass, 1955; Phillips, 1971; Felder, 1973). Concentrated in intertidal and shallow subtidal substrates ranging from sandy mud to organic silty sand, this fossorial species is adapted to oligohaline hab­ itats of coastal marshes, tidal channels, and estuarine embayments. Its range extends from western Florida through the Gulf states and southward at least to the Rio Carrizal estuary in Tamaulipas, Mexico. Osmoregu­ latory adaptations of adults and larvae have been documented (Felder, 1978; Felder et al., 1986), as have adaptations of the adults to periodic anoxia in their burrows (Felder, 1979). However, given the difficulty of monitoring natural populations in their fossorial habitats, little is known of growth, maturation, and reproduction in the species. The dominance of this species among the estuarine infauna, its role in marine food chains, its impact on plant and animal com­ munities, and its contribution to sediment and nutrient turnover likewise have re­ ceived little attention, though some of these qualities have been evaluated in popula­ tions of other western Atlantic thalassinoids