Protocols for monitoring wetland mitigation and restoration projects call for routine counts of animals, yet long-term spatial
and temporal patterns are rarely examined. An analysis of monitoring data from three southern California estuaries spanning
11 years, four seasons, and multiple stations within the estuaries revealed differences in spatio-temporal patterns between
fish and invertebrates. Ordination analysis showed that fish assemblages were more predictable from environmental variables
than were invertebrate assemblages. Variation in the fish assemblage was, primarily due to seasonal differences that were
driven by changes in temperature. Invertebrates showed little seasonal variation, but a much higher degree of interannual
variation than fish. Streamflow and dissolved oxygen were significant predictors of the invertebrate assemblage, indicating
that irregular disturbances such as flooding events had a more important effect on the invertebrate assemblage than predictable
seasonal cues such as temperature. Variation in fish and invertebrates was high both between and within the three estuaries,
indicating that differences exist on multiple spatial scales. The influence of spatial and temporal factors on estuarine invertebrate
and fish communities should be considered in planning monitoring programs for wetland mitigation or restoration sites.
Shinn et al. (2002) seem convinced that seepage meters are not a practical instrument to use in coastal environments for questions related to advection across the sediment-water interface. While their premise is certainly worth considering since so many scientific studies are tackling the issue of ground water discharge in recent decades, we disagree that they have sufficient evidence to support their conclusions. Their field experiments produced more technical questions for us about experimental design than answered questions concerning the magnitude of seepage rates in Florida Bay. The practicality of seepage meters as a measurement tool for ground water discharge is a persistent question. Seepage meters are easy to make and easy to use. Their simplicity alone worries some scientists. In many studies where multiple techniques have been applied or where control experiments have been performed in conjunction with field measurements, seepage meters provide consistent reliable results. We suggest some other questions to ask. What is the effect of altering the collection bag to seepage meter volume ratio on the anomalous short-term influx? Does that volume ratio control the magnitude of the hydraulic gradient between the bag and the seepage meter? How significant is the short-term influx when a 7-1 collection bag is placed in strong currents? How might this short-term influx be alleviated under different circumstances? How would the seepage results appear if tidal experiments were not performed as a net tidal effect, but instead evaluated seepage measurements on shorter time scales, such as less than a tidal cycle? The conclusions drawn by Shinn et al. (2002) are generalizations that are not very well supported by their experimental design or by their results. While their argument that Bernoulli's Principle affects seepage in this environment is not completely convincing, we agree that it may still be a contributing factor to some fraction of flow measurements. It is apparent (Fig. 1; Cable et al. 1997a; Chanton et al. 2003) that these devices respond to forces beyond the venturi effect. More quantitative work needs to be performed to assess this possible effect, as well as work to investigate its temporal and spatial variability and forces driving this flux. The measurements made by seepage meters, if made carefully and with some control experiments applied, are not artifacts. These measurements likely represent multiple water sources, such as infiltrating seawater and meteoric ground water fluxes. Mechanisms that drive pore water fluxes across the sediment-water interface may include wave-pumping (Bernoulli's principle applied), but experiments to test this mechanism and other possible driving forces need to be performed. Shinn et al. (2002) have given us all something to think about, but we suggest that some moderation of their conclusions is needed. We eagerly anticipate and actively work to elucidate the sources of water measured in coastal benthic advective studies.
Accretion rates were measured in fringe and basin mangrove forests in river and tidally dominated sites in Terminos Lagoon,
Mexico, and a basin mangrove forest in Rookery Bay, Florida, USA. Accretion rates were determined using the radionuclides210Pb and137Cs. Consolidation-corrected accretion rates for the Rookery Bay cores, ranged from 1.4 to 1.7 mm yr−1, with an average rate of 1.6 mm yr−1. Rates at the Mexico sites ranged from 1.0 to 4.4 mm yr−1, with an average of 2.4 mm yr−1. Determination of rates in these mangrove forests was greatly affected by the consolidation corrections which decreased the
apparent accretion rate by over 50% in one case. Accretion rates at basin sites compare favorably with a reported 1.4 to 1.6
mm yr−1 rate of sea-level rise, indicating little or no subsidence at inland locations. Accretion rates in fringe sites are generally
greater than basin sites, indicating greater subsidence rates in these sediments over longer time intervals.
Sediment profiles of210Pb and137Cs in cores collected at increasing distances from the heads of Smeaton Bay and Boca de Quadra fjords indicate that watersheds
influence the inventories of radioisotopes present and that the steep topographies of the fjords enhance sediment redistribution.
Episodic deposition of terrestrially derived sediment was responsible for roughly 50% of the137Cs and 45% of the210Pb inventories in shallower (less than 180 m) locations in Wilson and Bakewell arms of Smeaton Bay.210Pb sedimentation rates at shallower sites when corrected for episodic deposition were less than sedimentation rates obtained
in the deep basins of the fjords where sediment focusing and increased primary productivity in the overlying water column
occur. Higher fluxes of dissolved Mn from surficial sediments and subsequent reoxidation in the overlying water may have enhanced
scavenging of210Pb in basin locations, resulting in higher inventories. Episodic events have occurred frequently in Smeaton Bay and Boca de
Quadra suggesting that steady-state conditions with respect to sedimenting particles can be achieved only when averaged over
long time periods approaching the time over which137Cs and210Pb are useful.
We investigated the historical ecology of Elkhorn Slough, a 1,200 ha tidal wetland system in central California. The goal
of this study was to identify patterns of change in the extent and distribution of wetland habitats during a 150-yr period
and to investigate the causes of these changes. Using a geographic information system (GIS), we interpreted historic maps,
charts, and aerial photographs. We created a series of summary maps to illustrate and quantify changes in tidal flow and habitat
types at six representative historical periods. With the aid of custom software tools, we performed semi-automated spatial
analysis of historic aerial photographs to quantify changes in marsh cover at fixed quadrats and tidal creek width at fixed
cross sections. Our multiscale analysis documents dramatic shifts in the distribution of habitat types resulting from anthropogenic
modifications to the hydrology of the slough. More than half of the marshlands were diked, and more than two thirds have either
degraded or been converted to other habitat types. The construction of an artificial mouth abruptly transformed the wetland
system from depositional to highly erosional, enlarging channels, widening creeks, and converting marsh to intertidal mudflat
or open water. Increased tidal amplitude and velocity are the likely causes. In recent decades, levee failure and intentional
breaching have restored the acreage under tidal influence to nearly historic levels, but recolonization of former wetlands
by salt marsh vegetation has been minimal. Degraded former marshland and unvegetated mudflat are now the dominant habitat
types at Elkhorn Slough. The rate of habitat change remains high, suggesting that a new equilibrium may not be reached for
many decades. This study can help tidal wetland managers identify patterns and mechanisms of habitat change and set appropriate
conservation and restoration goals.
Adult horseshoe crabs,Limulus polyphemus, were tagged in the Middle Atlantic Bight area, from New York to Virginia on the continental shelf and within bays, to determine
their migratory patterns and longevity. Of 30,432 horreshoe crabs that were tagged during the years 1986–2002, 1,122 were
recovered alive, and 1,027 were dead. Many of the live recoveries were observed within 30 d (54.4%) and after years (37.53%)
with one tagged animal surviving up to 10 yr. In 9 locations from Great Kills Harbor, New York, to Chesapeake Bay, Maryland,
the horseshoe crabs return to their release beach within days during the spawning season. Of the 762 (100%) recoveries from
crabs released along the Delaware Bay shoreline, 75.07% traveled 0–20 km, 21.0% traveled 20–50 km, 2.36% traveled 50–100 km,
and 1.57% traveled over 100 km. Within Delaware Bay, 327 tagged animals (43.6%) had moved away from the release points to
other locations, and 59 of these had moved out of the bay onto the continental shelf along the Mid-Atlantic Bight coastline.
Horseshoe crabs migrate into Delaware Bay from waters off Ocean City, Maryland, and adjacent coastal bays. In addition to
defining the range of the Delaware Bay spawning populations, 2 neighboring populations were identified by the tagging program.
In one, animals tagged in southern New York mingled with those in the Sandy, Hook, New Jersey area, comprising a population
that ranged from Raritan Bay across New York Harbor to Jamaica Bay. The second confirmed that a discrete population existed
in northern Chesapeake Bay in the general vicinity of the Annapolis Bay Bridge.
The bivalve Pisidium amnicum (Müller 1774) is a common species in several European freshwater ecosystems. However, few Iberian watersheds are colonized
by this species, and the River Minho estuary is possibly the Iberian aquatic ecosystem with the larger population. In October
2004–2007, investigations on spatial and temporal variations in P. amnicum abundance and biomass were carried out at 16 sites along the River Minho tidal freshwater wetlands. Mean abundance and biomass
per site ranged from 0 to 750ind m−2 and 0 to 7.42g AFDW m−2, respectively. A clear decrease in the spatial distribution, abundance, and biomass was observed during the 4-year assessment.
Furthermore, a stepwise multiple regression model showed that organic matter and conductivity explained 50.2% of the variation
in P. amnicum abundance (R
2 = 0.502, F
[2, 15] = 7.569, p = 0.005). Ecological knowledge is essential to the implementation of future conservation plans for P. amnicum, and the results of this study are of paramount importance to identify habitats that should be protected in order to preserve
this species and provide scientific reference that may be useful in the development of management and/or restoration plans.
Following the May 18, 1980 eruption of Mount St. Helens, up to 11.5 cm of volcanic ash was deposited in sections of the upper
Columbia River estuary. A survey of the benthic infauna of this area indicates that most taxa were able to inhabit the ash,
suggesting that the material is nontoxic to most groups. However, the abundance of the taxa examined was dependent on the
distribution of the ash within the sediment column. Except for the oligochaetes, animal densites were reduced in areas where
volcanic ash lay atop the sediment surface as compared to areas where the ash layer had been buried beneath, or mixed with
sands and/or muds. The ash apparently affects the infauna through some physical means, possibly related to its fine grain
Nutrient loading to estuaries with heavily populated watersheds can have profound ecological consequences. In evaluating policy
options for managing nitrogen (N), it is helpful to understand current and historic spatial loading patterns to the system.
We modeled N inputs to Narragansett Bay from 1850 to 2000, using data on population, human waste disposal, livestock, fertilizer,
and atmospheric deposition. We found that total N loading to the bay increased 250% from 1850 to 2000, and 80% from 1900 to
2000. Loading to the upper bay increased far more than that to the lower bay, and the most important source shifted from non-point
animal waste to human waste concentrated at sewage treatment facilities. We also modeled future N loads in 2015 under four
management scenarios. Planned improvements in sewage treatment would reduce N loads 9% below business-as-usual, to the 1990
loading rate. Greater reductions, to circa 1900 rates of loading, may be possible.
KeywordsNitrogen-Agriculture-Sewage-Land use-Fertilizer-Atmospheric deposition
An analysis of Winslow’s 1878 oyster survey data of Tangier Sound relates the Euclidean dimensions of oyster beds to plan-channel
morphology, water depths, bottom slopes, and relief. Results show that at a regional scale the Tangier oyster beds followed
a benthic seascape density pattern related to the main axial Tangier Sound Channel: its morphology, meanders, and east-west
location. The north-south axis of the channel was intersected by estuarine flows into its central-eastern section, where meanders
began with a tight meander around a western shoal, followed by wider second and third meanders. The location of the deepest
axial depths of the channel’s bottom indicates a lateral, side-to-side switching between opposite beds, and a vertical undulation
in a deepening trend to 31 m at the apex of the first meander. The depth then generally shallowed as the channel plan-form
meandered southward to the sound’s entrance. Oyster beds flanked the upper sides of the channel, their generally long and
narrow linear axes oriented with that of the main channel in width-to-length ratios of <0.4. Bed lengths increased from the
north to the second meander, then decreased. The widest (2.3 km), longest (8.3 km), and largest (7 km2) beds laid opposite each other in the channel’s second meander. Eastern beds were generally wider and larger than western
beds, and water depths along their channel sides indicate a deepening trend from 3.6 m in the north to 16.5 m in the south,
unlike western beds, which reached a maximum depth of 10.4 m north of the meanders. Minimum water depths on the shoal sides
of beds varied little, described by mean values of 4.6 m (SD = 1.1) for eastern beds and 3.3 m (SD = 0.56) for western beds.
Analysis of profiles indicates that the deeper southeastern beds had variable relief with longer and more gradual slopes into
the channel than the shallower northwestern beds with flatter bed-tops and abrupt, steeper transitions into the channel. The
profiles indicate variability of a single bed in distributions of oysters and bed morphologies to make analysis at the small
scale difficult. However, at the regional scale, a seascape pattern emerges that relates the distributions of oysters to the
channel and shoals. This re-examination of the historic database in the context of regional tidal channel patterns provides
parameters for considering the interactive role of oysters with hydrodynamics and the structural importance of oyster reefs
for land and seascape processes.
The saltmarsh topminnow (Fundulus jenkinsi) is federally listed as a Species of Concern due to a its rarity, impacts from human activities, and lack of information
on its biology and ecology. From 2007 through 2008, we used Breder traps to fish the marsh edge on a falling tide in four
regions from Louisiana through the Florida panhandle during winter, spring, and summer periods. Out of 2,108 Breder traps
deployed, 661 F. jenkinsi were collected as far east as Escambia Bay, Florida, with Weeks Bay, National Estuarine Research Reserve (NERR), Alabama,
yielding the highest F. jenkinsi abundance. Principal component analysis (PCA) was used to ordinate physical–chemical data into two meaningful components:
a geomorphic axis (water depth, bank slope, and plant stem density) and a seasonal/spatial axis of species occurrence (water
temperature, salinity, and turbidity). PCA showed a higher mean catch-per-unit-effort (CPUE) in environments comprised of
low to moderate stem density (<25 stems/0.25m−2), depth (<25cm), bank slope (<15°), turbidity (<30NTU), and salinity (<16) coupled with spring and early summer water temperatures
(>15°C). F. jenkinsi CPUE was significantly higher in Spartina cynosuroides marsh edge compared with five other habitat types, even though it was one of the least sampled habitats. This species appears
to be collected more frequently and in higher CPUE in small dendritic creeks off of main channels than suggested by our previous
work in main channel edge habitat. This suggests that small creeks are important vectors for marsh access and supports the
value of the dendritic nature of salt marshes to marsh residents.
The blue crab, Callinectes sapidus Rathbun, 1896, represents the second most important fishery for coastal Georgia; yet, little is known about environmental
forces that affect planktonic postlarval settlement in the region. Here, we describe a study to examine the physical mechanisms
responsible for blue crab settlement in the extensive salt marsh system of coastal Georgia. Bottom and surface samplers were
placed at three sites along a salinity gradient from a low-salinity site in the Altamaha River to a high-salinity area of
the Duplin River, Sapelo Island, GA, USA during 2005. Megalopae and juvenile monitoring occurred from July through December.
The majority of both megalopae (86.8%) and juvenile (89.3%) blue crabs were recovered in bottom samplers at the low-salinity
Altamaha River site during August and early September. Few megalopae were collected at the surface of the Altamaha River or
at the two higher-salinity sites in the Duplin and North Rivers. Downwelling winds were unable to explain all settlement events;
however, winds with an onshore component regularly preceded settlement events. The use of a multiple-regression model revealed
a lagged relationship (r = 0.5461, $ lag = 0–2 days $ lag = 0–2 days ) between wind events, temperature, salinity, maximum tidal height, and settlement.
The regulation of shellfish and their growing waters is based on total and fecal coliform standards. Application of these
standards has reduced the incidence of shellfish-borne bacterial illnesses in humans, but outbreaks of viral diseases, such
as hepatitis A, Norwalk illness, and viral gastroenteritis, prevail. Hepatitis A virus contributed to 1,395 cases of shellfish-associated
illness since 1961. An additional 6,049 cases of shellfish-associated gastroenteritis were reported over the past 50 years,
75% of which (4,609 cases) occurred since 1980. The alarming rate of disease outbreaks during the past 5 years may further
increase as better reporting practices are initiated by health professionals and state and federal agencies. Actions necessary
to reduce the incidence of shellfish-associated viral illness include development of methods for detecting viral pathogens
in shellfish and harvest waters, correlation of levels of viral pathogens with potential viral and bacterial indicators, and
acceleration of field monitoring and enforcement efforts.
A 52-yr record of dissolved oxygen in Chesapeake Bay (1950–2001) and a record of nitrate (NO3
−) loading by the Susquehanna River spanning a longer period (1903, 1945–2001) were assembled to describe the long-term pattern
of hypoxia and anoxia in Chesapeake Bay and its relationship to NO3
− loading. The effect of freshwater inflow on NO3
− loading and hypoxia was also examined to characterize its effect at internannual and longer time scales. Year to year variability
in river flow accounted for some of the observed changes in hypoxic volume, but the long-term increase was not due to increased
river flow. From 1950–2001, the volume of hypoxic water in mid summer increased substantially and at an accelerating rate.
Predicted anoxic volume (DO<0.2 mg I−1) at average river flow increased from zero in 1950 to 3.6×109 m3 in 2001. Severe hypoxia (DO<1.0 mg I−1) increased from 1.6×109 to 6.5×109 m3 over the same period, while mild hypoxia (DO<2.0 mg I−1) increased from 3.4×109 to 9.2×109 m3. NO3
− concentrations in the Susquehanna River at Harrisburg, Pennsylvania, increased up to 3-fold from 1945 to a 1989 maximum and
declined through 2001. On a decadal average basis, the superposition of changes in river flow on the long-term increase in
− resulted in a 2-fold increase in NO3
− loading from the Susquehanna River during the 1960s to 1970s. Decadal average loads were subsequently stable through the
1990s. Hypoxia was positively correlated with NO3
− loading, but more extensive hypoxia was observed in recent years than would be expected from the observed relationship. The
results suggested that the Bay may have become more susceptible to NO3
− loading. To eliminate or greatly reduce anoxia will require reducing average annual total nitrogen loading to the Maryland
mainstem Bay to 50×106 kg yr−1, a reduction of 40% from recent levels.
Enumeration data from over 2,300 ichthyoplankton samples collected during 17 yr, spanning a 32-yr interval (1951–1983), were
compiled to determine interannual variations in density of sand lance larvae. Years of relatively high densities were noted
during the winters of 1965–1966 and 1978–1979 and low densities in 1971–1974. A regular increase in numbers during the late
1970’s and the peak in 1978–1979 coincided with increases in population size found throughout the coastal northwest Atlantic
Ocean. Densities in Long Island Sound began to decline in 1980 and this continued through 1983. In contrast, densities throughout
coastal Atlantic areas during the 1980’s remained at least as high as they were 1976–1978. Interannual fluctuations in density
of sand lance larvae could be partially explained by water temperatures in December. Warm Decembers were associated with low
Submerged aquatic plant populations in the Susquehanna Flats of the Chesapeake Bay were followed for 18 years. An exotic species,
eurasian water milfoil,Myriophyllum spicatum, increased dramatically from 1958 to 1962; at the same time the dominant native species declined. After 1962, milfoil populations
declined and the native rooted aquatics gradually began to return to their former levels. In the late 1960's all species declined
and in 1972 almost disappeared from the Susquehanna Flats. These fluctuations may have been related to several interrelated
environmental factors in the Chesapeake Bay, including tropical storms, turbidity, salinity and disease. The utilization of
the Susquehanna Flats by waterfowl appears to be related to the abundance and species composition of the submerged macrophytes
The Patuxent River, Maryland, is a nutrient-overenriched tributary of the Chesapeake Bay. Nutrient inputs from sewage outfalls
and nonpoint sources (NPS) have grown substantially during the last four decades, and chlorophylla levels have increased markedly with concomitant reductions in water quality and dissolved oxygen concentrations. The Patuxent
has gained national attention because it was one of the first river basins in the U.S. for which basin-wide nutrient control
standards were developed. These included a reduction in NPS inputs and a limit on both nitrogen (N) and phosphorus (P) loadings
in sewage discharges intended to return the river to 1950s conditions. Full implementation of point source controls occurred
by 1994, but population growth and land-use changes continue to increase total nutrient loadings to the river. The present
paper provides the perspectives of scientists who participated in studies of the Patuxent River and its estuary over the last
three decades, and who interacted with policy makers as decisions were made to develop a dual nutrient control strategy. Although
nutrient control measures have not yet resulted in dramatic increases in water quality, we believe that without them, more
extensive declines in water quality would have occurred. Future reductions will have to come from more effective NPS controls
since future point source loading will be difficult to further reduce with present technology. Changing land use will present
a challenge to policy makers faced with sprawling population growth and accelerated deforestation.
The calanoid copepod community was surveyed semi-monthly, from May to July 1992, at three stations in the Navesink-Shrewsbury
rivers system, the southernmost branch of the Hudson-Raritan estuary (New York-New Jersey). The dominant species collected
during the survey wasAcartia hudsonica, followed byA. tonsa. A comparison of this survey with three earlier surveys suggests that the calanoid copepod community and relative abundance
of dominant species have not changed substantially since the 1960s. Findings from a 1972 study, which noted the absence ofA. hudsonica andPseudodiaptomus coronatus as dominant species, were probably reflecting a temporary situation. The variations may have been related to a change in
water quality, caused by an upgrade in sewage treatment, completed just prior to the 1972 survey, and/or resulted from the
residual effects of Tropical Storm Agnes on this estuary.
Thirty-three ospreys (Pandion haliaetus) that were found dead or moribund in the Eastern United States between 1964 and 1973 were necropsied. The brains and carcasses
of 26 of these birds were analyzed for organochlorines. The livers of 18 and the kidneys of 7 were analyzed for selected metals.
Most adults were recovered in April and May and most immatures were recovered in August through October. The adult sex ratio
was highly unbalanced in favor of females. Major causes of mortality were impact injuries, emaciation, shooting, and respiratory
infections. Of special interest were two birds with malignant tumors and one with steatitis. Many birds had undergone marked
weight losses resulting in mobilization and redistribution of organochlorine residues. Organochlorines were detected in the
birds at the following percentages: DDE 100%, PCB 96%, DDD 92%, dieldrin 88%, chlordanes (including nonachlors) 82%, DDT 65%,
and heptachlor expoxide 38%. Organochlorine levels tended to be higher in adults than in immatures. One adult from South Carolina
had a potentially dangerous level of dieldrin in its brain, which might have contributed to its death. Immature ospreys from
Maryland had extremely elevated levels of copper in their livers compared with immatures from other areas and all adults.
One immature from Maryland had an elevated level of arsenic in its liver, which might have contributed to its death. One adult
from Florida that had died of impact injuries had potentially dangerous levels of mercury in both liver and kidney and slightly
elevated levels of cadmium in these tissues. Additional birds appeared to have been exposed to contamination of the environment
by arsenic and mercury. The levels of chromium, zinc, and lead in livers appeared normal.
Between 1966 and 1976, the Susquehanna River at Conowingo, Maryland, discharged approximately 50 million metric tons of suspended
sediment to Northern Chesapeake Bay. About 40 million metric tons were discharged in two floods associated with hurricanes:
Agnes (24–30 June 1972) and Eloise (26–30 September 1975). In the six years with complete records and no major floods, the
Susquehanna River discharged 0.9±0.3 million metric tons of suspended sediment per year at Conowingo Dam. Aout 50 to 60 percent
of the annual sediment discharge is usually floods, suspended sediment transport at Harrisburg, Pennsylvania, exceeds sediment
discharge at Conowingo, Maryland, probably due to sediment deposition in the lower river and behind three hydroelectric dams.
Atlantic menhaden (Brevoortia tyrannus) is well known for its commercial and ecological importance and has been historically declining in the Chesapeake Bay (Maryland),
one of its principal nursery habitats along the eastern coast. Using data from the Striped Bass Seine Survey of the Maryland
Department of Natural Resources (2003), we evaluated how the distribution of Atlantic menhaden has changed from 1966 to 2004
for 12 river drainages. We observed significant or marginally significant declines in 42% of the drainages, with drainages
of the northern Bay showing the majority of those declines. Continued recruitment to several drainages of the Bay may partly
explain why the adult spawning population is not declining. We determined if temporal changes in abundance were related to
changes in salinity or water quality for five major drainages of the watershed. For one of these drainages, the Patuxent River,
differences in productivity across sites largely explained differences in abundance. For the four remaining drainages, differences
in recruitment could not be explained by productivity or salinity gradients. While reducing nitrogen loading and enhancing
water clarity may improve Atlantic menhaden production, we suggest that the role of offshore processes on large-scale declines
has been largely neglected and studies on larval ingression are necessary for further elucidation of spatial and temporal
patterns of juvenile distribution in the Chesapeake Bay.
Maryland commercial landings of the blue crab (Callinectes sapidus) and catch per unit effort (CPUE) have remained fairly stable over the past 33 yr despite occasional large deviations from
the long-term average. During this time, however, significant declines in the percent of legal male crabs and the mean size
of legal males caught in fishery-independent surveys near Calvert Cliffs, Maryland have become apparent. Sublegal females
and two of the three legal female classes (152–177 and >178 mm CW) showed no significant trends over this 33-yr period when
examined by linear regression. Males showed significant trends for all size classes. Sublegal males increased from 24% of
the male population during the first 5 yr of the study (1968–1972) to 71% during 1996–2000. All classes of legal males, however,
exhibited downward trends. Males 127–151 mm CW decreased from 45% of the male population in the earliest period to 22% during
the last 5 yr. Males 152–177 mm decreased from 27% during 1968–1972 to only 6% during 1996–2000, and males > 178 mm declined
from 4% in the earliest period to 0.5% in the recent period. These size decreases for the most valuable portion of the blue
crab population are further evidence of over-exploitation. The declining trends in male size indicate that growth overfishing
is occurring as intense fishing pressure removes so many male crabs from the population as they reach legal size that few
remain to molt to larger size. A 3-yr data set from the Patuxent River, where commercial use of crab pots is restricted and
fishing pressure is lower, suggests that legal male crabs are able to attain larger size compared to an area where the pot
fishery is intense. A recommendation could be made for reducing effort where the pot fishery is intense by means of time,
gear, catch limits, and/or by increasing the minimum size of legal crabs to allow larger crabs to enter the fishery.
Long-term monitoring of water quality and phytoplankton was conducted at 19 sampling stations in Harima-Nada, eastern Seto
Inland Sea, Japan for 35years from 1973 to 2007. There were two significant long-term changes, an increase in winter water
temperatures of 0.042°C year−1, and a decrease in dissolved inorganic nitrogen (DIN) from about 10μM in the 1970s to ~5μM in the late 1990s due to the
reduction in nutrient inputs. DIN concentrations and total phytoplankton cell density were both higher during the 1970s to
the early 1980s and then exhibited a significant decrease in the mid 1980s and remained relatively constant thereafter. Diatoms
were the dominant phytoplankton group (>90%) over the 35-year period, and there was a dramatic shift from Skeletonema dominance (~70%) to Chaetoceros in the mid 1980s. This shift in diatom species may be attributed to differences in the life cycle of Skeletonema and Chaetoceros and the response to the decrease in DIN concentration.
-Diatoms-Nutrients-Phytoplankton dynamics-Seto Inland Sea-
Food habits of the dominant fishes collected from 1974 to 1980 at eight locations in Elkhorn Slough, California, and the adjacent
ocean were investigated. Epifaunal crustacea was the major prey group identified from stomach contents of more than 2,000
fishes, followed by epifaunal and infaunal worms, and molluscs. Overall, 18 fish species consumed 263 different prey taxa,
ranging from 10 taxa to 125 taxa per fish species and including 99 crustacean, 56 polychaete, and 39 molluscan taxa. Mean
prey richness was greatest at stations near the ocean and lowest at inshore stations. Detailed dietary data for all prey taxa
were summarized as trophic spectra for each fish species. Trophic spectra represented functional groups of prey and were used
for comparisons of dietary similarity. Cluster analyses, based on trophic spectra, resulted in four feeding guilds of fishes.
Of 18 fish species, seven (Amphistichus argenteus, Leptocottus armatus, Embiotoca jacksoni, Clevelandia ios, Gillichthys mirabilis, Cymatogaster aggregata, andCitharichthys stimaeus) fed principally on epifaunal crustacea. Four species (Pleuronectes vetulus, Platichthys stellatus, Phanerodon furcatus, andMyliobatus californica) consumed mostly molluscs and infaunal worms. Two species (Psettichthys melanostictus andTriakis semifasciata) fed on mobile crustacea, and five species (Hyperprosopon anale, Engraulis mordax, Clupea pallasi, Atherinopsis californiensis, andAtherinops affinis) fed largely on zooplankton and plant material. Our results suggest that high food availability enhances the nursery function
of imshore habitats, and emphasize the importance of invertebrate prey populations and the indirect linkage of plant production
to the ichthyofaunal assemblarly marine immigrant species that are likely ‘estuarine dependent’.
We determined the monthly and annual riverine freshwater, nitrogen (N) and phosphorus (P) loading into the North Sea from
Belgium, The Netherlands, and Germany for the years 1977–2000. An average of 133 km3 yr−1 of the 309 km3 yr−1 precipitation into the watershed is carried by the rivers into the sea. Total freshwater discharge fluctuates with a strong
6–7 yr periodicity, is strongly correlated with precipitation, and exhibits a slight long-term decrease. The temporal changes
of regional patterns of precipitation lead to changing ratios of annual discharge of the western rivers compared to the eastern
rivers, varying between 2.2 and 3.5. The long-term oscillations in discharge were more pronounced as discharge increased.
The annual means of total and dissolved inorganic N and P loads were estimated to be 722 and 582 kt N yr−1 and 48 and 26 kt P yr−1, respectively. The monthly N loads were much more strongly correlated with discharge, compared to the monthly P loads. Total
N and P as well as dissolved inorganic N also demonstrated a 6–7 yr periodicity. The annual N loads decreased by about 17
kt N yr−1 from 1977 to 2000. The total phosphorus and phosphate loads decreased from about 80 and 50 kt P yr−1 in the 1980s to 25 and 12 kt P yr−1, respectively, in the 1990s. The western rivers contributed the major part of the nutrient loads. The long-term oscillations
in their nutrient loads were much more pronounced, compared to the eastern rivers. The area-specific loading rates estimated
for all rivers are comparable to earlier estimates using shorter data records, smaller sample sizes, and a less complete watershed
monitoring program. The monthly and annual average N:P ratios and their variability increased considerably for individual
rivers during the study interval. These results confirm that the water quality of European continental rivers is strongly
influenced by intense land use. They demonstrate the necessity for using long time series monitoring results to assess change
and evaluate the effects of climate change on the North Sea coastal ecosystems, using ecosystem models on decadal time scales.
We investigated whether climate change results in long-term changes in phytoplankton biomass and phenology in a turbid eutrophic
coastal plain estuary. Changes in annual mean chlorophyll a (chla) concentrations were studied for the period 1978–2006 in the eutrophic and turbid macro-tidal Western Scheldt estuary. Three
stations were investigated: WS1, at the mouth of the estuary; station WS6, halfway up the estuary; and station WS11, near
the Dutch–Belgian border near the upstream end of the estuary. No significant long-term changes in yearly averaged chla concentrations were observed in WS1 and WS6, but in WS11 the phytoplankton biomass decreased considerably. This is most likely
due to an increase in grazing pressure as a result of an improvement in the dissolved oxygen concentrations. Spectral analyses
revealed a possible periodicity of 7years in the mean chla which was related to periodicity in river discharge. We also observed strong phenological responses in the timing of the
spring/summer bloom which were related to a well-documented increase in the temperature in the estuary. The fulcrum, the center
of gravity or the day at which 50% of the cumulative chla was reached during the year, advanced by 1–2days/year. A similar trend was observed for the month in which the maximum bloom
was observed, with the exception of station WS1. All stations showed an earlier initiation of the bloom, whereas the day at
which the phytoplankton bloom was terminated also moved forward in time excepted for WS11. As a result, the bloom length decreased
at station WS1, remained the same at station WS6, and increased at WS11. This complicated pattern in bloom phenology demonstrates
the complex nature of ecosystem functioning in estuaries.
-Times series-Phenology-Phytoplankton biomass-Western Scheldt estuary
During the year 1978, juvenile salmonids were collected from coastal streams running through China Poot Marsh and the stomach
contents analyzed. Stomach contents of threespine stickleback (Gasterosteus aculeatus) and staghorn sculpin (Leptocottus armatus) from China Poot and of threespine stickleback from Potter Marsh were also analyzed; these two species were generally caught
in tidal pools on the marshes. The juvenile coho salmon (Oncorhynchus kisutch) had the most varied diet; 37 different prey items were identified in the stomachs. By comparison, 25, 26, and 33 prey taxa
were identified in the stomach contents of Dolly Varden char (Salvelinus malma), threespine stickleback, and staghorn sculpin, respectively. Amphipods were the dominant prey of all fish collected from
China Poot Marsh; chironomidae larvae were the most common item in the stomach contents of threespine stickleback from Potter
Marsh. The diets of all species changed over the course of the study period; the change was most dramatic for juvenile salmonids
Monthly growth of the fouling community at eight test panel sites in the Loxahatchee River Estuary was related to salinity
and temperature. Growth was lowest in January 1981 (averaging 23 g per m2, dry weight), and increased during spring and early summer with increasing water temperature. Maximum growth occurred during
early or midsummer at upstream locations, before river or canal discharge substantially reduced salinity, and in late summer
at downstream locations. Growth was greatest at salinities slightly less than that of seawater and decreased at salinities
less than about 10‰. Growth was suppressed throughout the estuary in August 1981, probably because of the sudden decrease
in temperature and salinity, and perhaps the increase in physical scouring, caused by runoff from Tropical Storm Dennis. Large
loads of nutrients transported to the estuary from storm runoff, however, may have subsequently stimulated growth, which increased
in September 1981 to the maximum for the year (averaging 683 g per m2, dry weight).
We analyzed monthly boat electrofishing data to characterize the littoral fish assemblages of five regions of the Sacramento-San
Joaquin Delta (northern, southern, eastern, western, and central), California, during two sampling periods, 1980–1983 (1980s)
and 2001–2003 (2000s), to provide information pertinent to the restoration of fish populations in this highly altered estuary.
During the 1980s, almost 11,000 fish were captured, including 13 native species and 24 alien species. During the 2000s, just
over 39,000 fish were captured, including 15 native species and 24 alien species. Catch per unit effort (CPUE) of total fish,
alien fish, and centrarchid fish were greater in the 2000s compared with the 1980s, largely because of increased centrarchid
fish CPUE. These differences in CPUE were associated with the spread of submerged aquatic vegetation (SAV), particularly an
alien aquatic macrophyte,Egeria densa. Native fish CPUE declined from the 1980s to the 2000s, but there was no single factor that could explain the decline. Native
fish were most abundant in the northern region during both sampling periods. Nonmetric multidimensional scaling indicated
similar patterns of fish assemblage composition during the two sampling periods, with the northern and western regions characterized
by the presence of native species. The separation of the northern and western regions from the other regions was most distinct
in the 2000s. Our results suggest that native fish restoration efforts will be most successful in the northern portion of
the Delta. Management decisions on the Delta should include consideration of possible effects on SAV in littoral habitats
and the associated fish assemblages and ecological processes.
Fish abundance and environmental data collected over ten years (1980–1989) from the middle Thames estuary, England, were analyzed
to detect temporal trends in fish populations and relationship with environmental parameters, and to assess water quality.
Fish were collected from the cooling water intake screens of West Thurrock power station, situated 35.5 km below London Bridge,
in the mid-estuary. Marine species abundance were highly seasonal, with peaks in December–March for herring (Clupea harengus), sprat (Sprattus sprattus), 3-spined-stickleback (Gasterosteus aculeatus), and poor cod (Trisopterus minutus); July–August for flounder (Platichthys flesus); and September–December for sand goby (Pomatoschistus minutus), whiting (Merlangius merlangus), bass (Dicentrarchus labrax), plaice (Pleuronectes platessa), and dab (Limanda limanda). Bimodal seasonal patterns of peaks or unclear seasonality in abundance characterized marine estuarine-dependent sole (Solea solea), Nilsson's pipefish (Syngnathus rostelattus) (April/May and September/October), and pouting (Trisopterus luscus) (May and November/December); the estuarine smelt (Osmerus eperlanus) (October and January) and the catadromous eel (Anguilla anguilla) (June and October). There was substantial variation in the abundance of common species over the period of ten years, with
herring, sand goby, flounder, and plaice showing a stable abundance in 1980–1984, increasing sharply in 1985–1986, and then
decreasing successively through the remainder of the decade (1987–1989). The first half of the decade was a period of higher
abundance for less tolerant species such as smelt, sprat, and poor cod, while the second half showed higher abundances of
species tolerant to harsh environmental conditions such as sand goby, flounder, eel, and plaice. A general pattern of stable
fish populations with a slight trend of deterioration was found to emerge over the years, related to the number of species
and quantities of common species. Multivariate techniques of principal component and canonical correspondence ordinations
were used for assessing relationships between fish populations abundance and environmental variables. The most significant
environmental variables correlated with fish species were temperature and dissolved oxygen. High abundances of flounder were
associated with high temperature, while high abundance of poor cod, sprat, herring, and 3-spined-stickleback were associated
with high dissolved oxygen, flow, ammonical nitrogen, and low temperature. Plaice, whiting, sand goby, bass, and dab were
preferentially found in high salinity and suspended solids, while smelt and sole were likely to prefer average values or showed
no clear preferences.
Meteorological impacts of El Niño events of 1982–1983 and 1997–1998 were observed in locations throughout the world. In southern
Brazil, El Niño events are associated with increased rainfall and higher freshwater discharge into Patos Lagoon, a large coastal
lagoon that empties into the Atlantic Ocean. Based on interdecadal meteorological and biological data sets encompassing the
two strongest El Niño events of the last 50 yr, we evaluated the hypothesis that El Niño-induced hydrological changes are
a major driving force controlling the interannual variation in the structure and dynamics of fishes in the Patos Lagoon estuary.
High rainfall in the drainage basin of the lagoon coincided with low salinity in the estuarine area during both El Niño episodes.
Total rainfall in the drainage basin was higher (767 versus 711 mm) and near-zero salinity conditions in the estuarine area
lasted about 3 mo longer during the 1997–1998 El Niño event compared with the 1982–1983 event. Hydrological changes triggered
by both El Niño events had similar relationships to fish species composition and diversity patterns, but the 1997–1998 event
appeared to have stronger effects on the species assemblage. Although shifts in species composition were qualitatively similar
during the two El Niño events, distance between El Niño and non-El Niño assemblage multivariate centroids was greater during
the 1996–2000 sampling period compared with the 1979–1983 period. We provide a conceptual model of the principal mechanisms
and processes connecting the atmospheric-oceanographic interactions triggered by the El Niño phenomena and their effect on
the estuarine fish assemblage.
Analysis of current and salinity time series from early 1982 over the inner shelf near the Texas-Louisiana border indicates
a rapid freshening of the coastal current waters in response to the discharge of the Mississippi River. Coherence between
records is surprisingly poor, although cross-shelf advection of the salinity front by tidal advection appears to be an important
A retrospective analysis of freshwater discharge, riverine dissolved nutrient loads, dissolved nutrients, and chlorophyll in the Chesapeake Bay from 1985 to 2008 is presented. It is evident that each field displays an interannual variability averaged over the Bay. The N and P loads peaked in 1997 and have fluctuated with a decreasing trend since early 2004. Dissolved nutrient concentrations in the Bay appear to be largely controlled by riverine nutrient loads. The temporal variability of chlorophyll is positively correlated with nutrient loads and concentrations. Over the study period, N:P (DIN:DIP) molar ratios were consistently higher than the Redfield ratio (N:P = 16:1) and strongly correlated with river discharge (R
2 = 0.68, p < 0.05) with high discharge periods corresponding to high DIN levels. The N:P stoichiometric analysis indicates that P is the limiting nutrient in spring (N:P > 16:1), and N is the limiting nutrient in summer and early autumn (N:P < 16:1), pointing to an uptake of dissolved nitrogen by the phytoplankton and the release of PO4 from anoxic sediments. Long-term climate indices, such as El Niño Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), appear to exert only a moderate control over the riverine discharge to the Bay or over the ecosystem response in terms of chlorophyll in the Bay. While not all related mechanisms can be inferred from available data, this analysis should help in determining future data needs for monitoring water quality and human and climate influence on the health of the Bay.
In the Tampa Bay region of Florida, extreme levels of annual and seasonal rainfall are often associated with tropical cyclones
and strong El Niño episodes. We used stepwise multiple regression models to describe associations between annual and seasonal
rainfall levels and annual, bay-segment mean water clarity (as Secchi depth [m]), chlorophylla (μg I−1), color (pcu), and turbidity (ntu) over a 20-yr period (1985–2004) during which estimated nutrient loadings have been dominated
by non-point sources. For most bay segments, variations in annual mean water clarity were associated with variations in chlorophylla concentrations, which were associated in turn with annual or seasonal rainfall. In two bay segments these associations with
annual rainfall were superimposed on significant long-term declining trends in chlorophylla. Color was significantly associated with annual rainfall in all bay segments, and in one segment variations in color were
the best predictors of variations in water clarity. Turbidity showed a declining trend over time in all bay segments and no
association with annual rainfall, and was significantly associated with variations in water clarity in only one bay segment.
While chlorophylla, color, and turbidity a affected water clarity to varying degrees, the effects of extreme rainfall events (El Niño events
in 1998 and 2003, and multiple tropical cyclone events in 2004) on water clarity were relatively short-lived, persisting for
periods of months rather than years. During the 20-yr period addressed in these analyses, declining temporal trends in chlorophylla and turbidity, produced in part by a long-term watershed management program that has focused on curtailing annual loadings
of nitrogen and other pollutants, may have helped to prevent the bay as a whole from responding more adversely to the high
rainfall periods that occurred in 1998 and 2003–2004.
The temporal distributions for six classes of trace organic contaminants (chlordanes, DDTs, dieldrin, PAHs, PCBs, and butyltins)
in oysters from six Galveston Bay sites from National Oceanic and Atmospheric Administration’s National Status and Trends
(NS&T) Mussel Watch Program are compared with other NS&T sites from the Gulf of Mexico as well as all NS&T sites of the United
States (East Coast, West Coast, and Gulf of Mexico). Decreases in the median for the Gulf-wide concentration of chlordanes,
dieldrin, and butyltins occurred during 1986–1994. The Gulfwide median concentrations of DDTs, PAHs, and PCBs exhibited a
strong cyclic distribution with time. For Galveston Bay oysters, “high” concentration is defined as the concentration greater
than the median plus one standard deviation for all Gulf of Mexico sites. The percentage of sites having high concentrations
during 1986–1994 for Galveston Bay oysters are 49% for dieldrin, 45% for butyltins, 40% for chlordanes, 38% for PCBs, 30%
for PAHs, and 21% for DDTs. For PCBs, 43% of Galveston Bay oyster samples analyzed over the first 9 yr have concentrations
high enough for potential biological effects to be observed in oysters. The percentages in other agents were chlordanes (22%),
butyltins (22%), dieldrin (5%), and PAHs (4%). National Academy of Science-proposed regulatory limits for oysters were exceeded
in only 2% of Galveston Bay samples for DDTs and 1% for PCBs. All other contaminants were below proposed NAS limits.
We analyzed trends in a 23-year period of water quality and biotic data for Chesapeake Bay. Indicators were used to detect
trends of improving and worsening environmental health in 15 regions and 70 segments of the bay and to assess the estuarine
ecosystem’s responses to reduced nutrient loading from point (i.e., sewage treatment facilities) and non-point (e.g., agricultural
and urban land use) sources. Despite extensive restoration efforts, ecological health-related water quality (chlorophyll-a,
dissolved oxygen, Secchi depth) and biotic (phytoplankton and benthic indices) metrics evaluated herein have generally shown
little improvement (submerged aquatic vegetation was an exception), and water clarity and chlorophyll-a have considerably
worsened since 1986. Nutrient and sediment inputs from higher-than-average annual flows after 1992 combined with those from
highly developed Coastal Plain areas and compromised ecosystem resiliency are important factors responsible for worsening
chlorophyll-a and Secchi depth trends in mesohaline and polyhaline zones from 1986 to 2008.
KeywordsBiotic-Chesapeake Bay-Eutrophication-Health indices-Water quality
Estuarine nursery areas are critical for successful recruitment of tautog (Tautoga onitis), yet they have not been studied over most of this species' range. Distribution, abundance and habitat characteristics of
young-of-the-year (YOY, age 0) and age 1+juvenile tautog were evaluated during 1988–1992 in the Narragansett Bay estuary,
Rhode Island, using a 16-station, beach-seine survey. Estuary-wide abundance was similar among years. Greatest numbers of
juveniles were collected at northern Narragansett Bay stations between July and September. Juvenile abundances varied with
density of macroalgal and eelgrass cover; abundances ranged from 0.03 fish per 100 m2 to 8.1 fish per 100 m2. Although juveniles use eelgrass, macroalgae is the dominant vegetative cover in Narragansett Bay. Macroalgal habitats play
a previously unrealized, important role and contribute to successful recruitment of juvenile tautog in Narragansett Bay. Juvenile
abundances did not vary with sediment type or salinity, but were correlated with surface water temperature. Fish collected
in June were age 1+ juveniles from the previous year-class (50–167 mm TL) and these declined in number after July or August.
The appearance of YOY (25–30 mm TL) in July and August was coincident with the period of their greatest abundances. A precipitous
decline in abundance occurred by October because of the individual or combined effects of mortality and movement to alternative
habitats. Based on juvenile abundance, a previously unidentified spawning area was noted in Mount Hope Bay, a smaller embayment
attached to the northeastern portion of Narragansett Bay. In August 1991, Hurricane Bob disrupted juvenile sise distribution
and abundance, resulting in reduced numbers of YOY collected after the storm and few 1+ juveniles in 1992.
Analysis of 6 yr of monthly water quality data was performed on three distinct zones of Florida Bay: the eastern bay, central
bay, and western bay. Each zone was analyzed for trends at intra-annual (seasonal), interannual (oscillation), and long-term
(monotonic) scales. the variables TON, TOC, temperature, and TN∶TP ratio had seasonal maxima in the summer rainy season; APA
and Chla, indicators of the size and activity of the microplankton tended to have maxima in the fall. In contrast, NO3
+, turbidity, and DOsat, were highest in the winter dry season. There were large changes in some of the water quality variables of Florida Bay over
the study period. Salinity and TP concentrations declined baywide while turbidity increased dramatically. Salinity declined
in the eastern, central, and western Florida Bay by 13.6‰, 11.6‰, and 5.6‰, respectively. Some of the decrease in the eastern
bay could be accounted for by increased freshwater flows from the Everglades. In contrast to most other estuarine systems,
increased runoff may have been partially responsible for the decrease in TP concentrations as input concentrations were 0.3–0.5
μM. Turbidity in the eastern bay increased twofold from 1991 to 1996, while in the central and western bays it increased by
factors of 20 and 4, respectively. Chla concentrations were particularly dynamic and spatially heterogeneous. In the eastern bay, which makes up roughly half of
the surface area of Florida Bay, Chla declined by 0.9 μg l−1 (63%). The hydrographically isolated central bay zone underwent a fivefold increase in phytoplankton biomass from 1989 to
1994, then rapidly declined to previous levels by 1996. In western Florida Bay there was a significant increase in Chla, yet median concentrations of Chla in the water column remained modest (∼2 μg l−1) by most estuarine standards. Only in the central bay did the DIN pool increase substantially (threefold to sixfold). Notably,
these changes in turbidity and phytoplankton biomass occurred after the poorly-understood seagrass die-off in 1987. It is
likely the death and decomposition of large amounts of seagrass biomass can at least partially explain some of the changes
in water quality of Florida Bay, but the connections are temporally disjoint and the process indirect and not well understood.
An ichthyoplankton survey (18 stations in seven sampling sectors) was conducted in Narragansett Bay in 1990 to provide information
on abundance, distribution, and seasonal occurrence of eggs and larvae of estuarine fishes, including seasonal migrants. An
additional goal was to examine changes in species composition, abundance, and distribution occurring since the last baywide
survey in 1972–73. The taxonomic composition of eggs and larvae in 1990 (41 species in 25 families from 684 plankton samples)
and in 1972–73 (43 species in 28 families from 6900 samples) was similar. Maximum abundance of fish eggs occurred in June
and larvae in July, minimum abundance in September to February. Species diversity was greatest in May–July and lowest during
January in both surveys. However, egg and larval densities in 1990 were considerably lower than in 1972–73. Bay anchovy, tautog,
and cunner accounted for 86% of the eggs and 87% of the larvae in the bay in 1990. These three species accounted for only
55% of the eggs and 51% of the larvae in 1972–73, with menhaden accounting for another 18% of the eggs and 34% of the larvae.
Searobins, scup, and butterfish eggs were common in 1973 (19%) but rare in 1990 (2%). Ichthyoplankton abundance for several
of the most abundant species was significantly lower (p<0.05) in the Providence River, upper bay, and Greenwich Bay in 1990
than in 1972–73. Density of fish eggs and larvae in the lower portions of the bay was lower in 1990 for some species but not
others. Distribution data suggested a general down-bay shift in density in 1990. *** DIRECT SUPPORT *** A01BY085 00015
Late summer hypoxia (<3 ppm oxygen) in western Long Island Sound (WLIS) is a persistent environmental and management issue
whose controlling processes are poorly understood. Measured rates of sediment and water-column oxygen consumption in the bottom
water suggest that a condition of no oxygen should be attained on the time scale of 13–30 d. Observations, however, indicate
the onset of hypoxia is of the order 150 d. Therefore, horizontal and/or vertical transport of oxygen into the area of hypoxia
must play an important role. Hypoxia decreases benthic activity and the sediment flux of222Rn. The resulting horizontal gradient in bottom water222Rn was measured and used to estimate the effective horizontal transport rate (>5–50 m2 s−1), which is considerably slower than previous estimates. Scale analysis of the hypoxia process indicates that horizontal transport
rates alone can explain the slow progression of hypoxia in XLIS but that vertical processes may also be capable of delaying
the onset of hypoxia especially under conditions of weak stratification or weak intermediate layer oxygen consumption. This
scale analysis indicates a delicately balanced process that is sensitive to both climatologically-driven variability in the
rates of horizontal and vertical transport as well as the biologically-driven rates of oxygen consumption. An improved ability
to predict and/or control hypoxia must be based on a better understanding of temporal and spacial variations in circulation,
mixing, and stratification as well as the biological processes in the water column and the sediments.
A long-term study (monthly sampling, 1992 to 2007) was conducted in the surf zone of Cassino Beach, Southern Brazil, in order
to detect possible natural and/or anthropogenic disturbances. Surface water temperature (6–29°C) was the only parameter with
predictable seasonal variation; salinity (14–38) was inversely related to rainfall (3.1–485.2mm month−1) and low values followed extreme precipitation periods in 1997/1998 and 2002/2003 (El Niño years). Asterionellopsis glacialis and chlorophyll a presented high concentrations and peak frequency until 1998, when an intense mud deposition occurred with concomitant extreme
rainfall. It affected the surf zone and beach, changing the hydrology and dissolved inorganic nutrient availability. Six phytoplankton
species groups were recognized with distinct responses to this mud deposition. We conclude that large-scale climatic changes,
like El Niño Southern Oscillation, in conjunction with human activities significantly altered the phytoplankton ecology of
the highly dynamic Cassino Beach surf zone.
KeywordsSandy beach-Microalgae-Long term-El Niño-Mud deposition
The Massachusetts Water Resources Authority (MWRA) conducts a comprehensive multidisciplinary monitoring program in Massachusetts
Bay, Cape Cod Bay, and Boston Harbor to assess the environmental effects of a relocated secondary-treated effluent outfall.
Through 2007, 8.7years of baseline data and 7.3years of postdiversion data (16 total years), including species level estimates
of phytoplankton and zooplankton abundance, have been collected. MWRA’s monitoring program and other studies make this region
one of the most thoroughly studied and well-described marine systems in the world. The data show that the diversion of MWRA
effluent from the harbor to the bay has decreased nutrients concentrations and improved water quality in the harbor (e.g.,
higher dissolved oxygen, lower chlorophyll). The diversion also resulted in an increase in dissolved inorganic nutrients (especially
ammonium) in the vicinity of the bay outfall, but no obvious impacts such as increased biomass or decreased bottom water dissolved
oxygen have been observed. Regional changes in phytoplankton and zooplankton unrelated to the diversion have been seen, and
it is clear that the bays are closely connected both physically and ecologically with the greater Gulf of Maine. Direct responses
to modifications of the nutrient field within a 10 × 10-km area centered near the midpoint of the 2-km long outfall diffuser
in Massachusetts Bay (a.k.a. the nearfield) have not been seen in the plankton community. However, plankton variability in
the bays has been linked to large regional to hemispheric scale (NAO) processes.
KeywordsMassachusetts Bay-Boston Harbor-NAO-Temporal and spatial trends-Phytoplankton-Zooplankton-Chlorophyll-Outfall-
-Phytoplankton time series
The influence of atmospheric forcing on the flow and heat transports in the lower Chesapeake Bay and the adjacent coastal
ocean were studied by comparing nontidal sea level and sea surface temperature variations in this region with meteorological
data for 1992. Northeasterly and southwesterly winds caused the greatest changes in mean sea level (greater than 0.25 m) throughout
the year. Northeastely winds caused a more rapid response than southwesterly winds, causing sea-level rises in less than 6
h. Barometric pressure changes typically contributed approximately 10% to extreme sea-level variations and were less influential
than wind stress in most cases. Wind forcing was also responsible for summer events in which the horizontal water temperature
gradient between two near-surface locations in the vicinity of the bay mouth vanished. These zero-gradient events corresponded
to inflows and outflows at the bay's entrance caused by northeasterly and southwesterly winds, respectively. Wind-induced
advection outside the lower Chesapeake Bay was additionally responsible for extreme heat flux variations. Heat gains and losses
during the spring and fall occurred in pulsating events related to wind direction but were probably not connected to lower
Sediment samples from 281 estuarine sites in the Gulf of Mexico were collected in 1993–1994 and analyzed for several classes
of organic and organometallic compounds as part of the Environmental Monitoring and Assessment Program of the United States
Environmental Protection Agency. Polynuclear aromatic hydrocarbons (PAHs) were the contaminant class found most frequently
and in the highest concentrations; the sum of 24 congeners (ΣPAHs) ranged from <5 ng g−1 to 15.500 ng g−1 (dry wt basis). A low percentage of samples (3.9%) exceeded 2000 ng g−1 ΣPAHs, and only six samples (2.1%) exceeded 4000 ng g−1, a level above which adverse biological effects may be expected to occur. Less than 4% of sediments exceeded 20 ng g−1 for the sum of 20 polychlorinated biphenyls (ΣPCBs) and only four samples (1.4%) exceeded 20 ng g−1 for the sum of several organochlorine pesticides (ΣOCPs). A sample from Freeport Harbor, Texas, contained 4230 ng g−1 ΣPAHs, 322 ng g−1 ΣPCBs, and 49.6 ng g−1 ΣOCPs. Tributyltin exceeded 100 ng g−1 in only four samples, all of which were from stations in Corpus Christi Bay or Galveston Bay in Texas. The detection of a
suite of organophosphate pesticides was very rare and did not exceed 15 ng g−1. Sediments from the tidally influenced section of the Mississippi River in Louisiana contained low to moderate levels of
all classes of organic compounds. The most contaminated sites were in urban estuaries (e.g., Corpus Christi, Galveston, and
Pensacola (Florida bays), underscoring the need to concentrate future monitoring and assessment efforts at the regional and
Within the KUSTOS program (Coastal Mass and Energy Fluxes-the Land-Sea Transition in the Southeastern North Sea) 28 to 36
German Bight stations were seasonally surveyed (summer 1994, spring 1995, winter 1995–1996) for light conditions, dissolved
inorganic nutrient concentrations, chlorophylla (chla), and photosynthesis versus light intensity (P:E) parameters. Combining P:E curve characteristics with irradiance, attenuation,
and chlorophyll data resulted in seasonal estimates of the spatial distribution of total primary production. These data were
used for an annual estimate of the total primary production in the Bight. In winter 1996 the water throughout the German Bight
was well mixed. Dissolved inorganic nutrient concentrations were relatively high (nitrogen [DIN], soluble reactive phosphorus
[SRP], and silicate [Si]: 23, 1, and 10 μM, respectively). Chla levels generally were low (< 2 μg l−1) with higher concentrations (4–16 μg l−1) in North Frisian coastal waters. Phytoplankton was limited by light. Total primary production averaged 0.2 g C m−2 d−1. Two surveys in April and May 1995 captured the buildup of a strong seasonal thermo-cline accompained by the development
of a typical spring diatom bloom. High nutrient levels in the mixed layer during the first survey (DIN, SRP, and Si: 46, 0.45,
and 11 μM, respectively) decreased towards the second survey (DIN, SRP, and Si: 30.5, 0.12, and 1.5 μM, respectively) and
average nutrient ratios shifted further towards highly imbalanced values (DIN:SRP: 136 in survey 1, 580 in survey 2; DIN:Si:
13.5 in survey 1, 96 in survey 2). Chla ranged from 2 to 16 μg l−1 for the first survey and rose to 12–50 μg l−1 in the second survey. Phytoplankton in nearshore areas continued to be light limited during the second survey, while data
from the stratified regions in the open German Bight indicates SRP and Si limitation. Total primary production ranged from
4.0 to 6.3 g C m−2 d−1. During summer 1994 a strong thermal stratification was present in the German Bight proper and shallow coastal areas showed
unusually warm (up to 22°C), mixed waters. Chla concentrations ranged from 2 to 18 μg l−1. P:E characteristics were relatively high despite the low nutrient regime (DIN, SRP, and Si: 2, 0.2, and 1.5 μM, respectively),
resulting in overall high total primary production values with an average of 7.7 g C m−2 d−1. Based on the seasonal primary production estimates of the described surveys a budget calculation yielded a total annual
production of 430 g C m−2 yr−1 for the German Bight.
Increasing physical oceanographic evidence suggests that a regime shift, which featured increased equatoward surface winds
and upwelling in the Eastern Pacific Boundary Current region, occurred following the 1997–1998 El Niño. We expect the signal
of this change in biota to be stronger in euphausiids than in pelagic fishes such as Pacific hake (Merluccius productus) because lower trophic levels are more responsive to changes in upwelling and primary production. We used acoustic backscatter
data from acoustic surveys in summer 1995, 1998, and 2001 to explore whether significant changes in abundance and distribution
of euphausiids and fishes have occurred between 1995 and 2001. Graphical and statistical results show that the density of
fish schools and euphausiid patches increased significantly south of Cape Blanco between 1995 and both 1998 and 2001. North
of Cape Blanco there was no consistent change in euphausiid abundance, although both fish and euphausiid distributions in
2001 appear to be significantly higher nearshore than in the other years. Pelagic fish abundance distributions appeared more
closely linked to El Niño than to regime shifts, with abundance shifted much farther north in 1998, an El Niño year, than
in the other years, while 1995 and 2001 fish abundance distributions are similar to each other. The regime shift appears so
far to have had a stronger effect on euphausiids than on pelagic fishes. The change in euphausiid abundance and distribution
between the survey years was linked, through a conceptual model, to the relative strength of the poleward flowing California
undercurrent and equatorward flowing California current and to the distribution and abundance of hake.
Data on hydrography, nutrients, suspended particles, and sedimented particles were collected at weekly intervals from November
to May during 1995 to 1997 at a station in the coastal waters of Dona Paula Bay, India. Suspended and sedimented particles
were analyzed for total suspended matter (SPM), total sedimented particulate matter (TPM), particulate organic carbon (POC),
particulate organic nitrogen (PON), chlorophylla (chla), and diatom abundance. Variations in hydrography and nutrients influenced the quantity and composition of sedimented particles.
The TPM, POC, PON, and chla fluxes showed small-scale seasonal variations and were higher in the summer (February to May) than in the winter (November
to January). Resuspension of carbon accounted for approximately 25% of the gross POC and was highest in April 1997 (45%).
The mean net POC flux was 197±90 mg C m−2 d−1 and accounts for 4.6% of the TPM. The average C∶N (w∶w) ratio of the sedimented material was 13.2±6.6. The POC:chla ratio was relatively higher in the sedimented material as compared to the suspended material. The particulate carbon reaching
the bottom sediment was 39% of the primary production. The low organic carbon concentration (approximately 0.1% of dry sediment)
in the sediments implies that about 98% of the sedimented carbon was either consumed at the sedimentwater interface or resuspended/advected
before it was finally buried into the sediments.
Estuaries receive large quantities of suspended sediments following the first major storm of the water year. The first-flush
events transport the majority of suspended sediments in any given year, and because of their relative freshness in the hydrologic
system, these sediments may carry a significant amount of the sediment-associated pesticide load transported into estuaries.
To characterize sediment-associated pesticides during a first-flush event, water and suspended sediment samples were collected
at the head of the San Francisco Bay during the peak in suspended sediment concentration that followed the first major storm
of the 1996 hydrologic year. Samples were analyzed for a variety of parameters as well as 19 pesticides and degradation products
that span a wide range of hydrophobicity. Tidal mixing at the head of the estuary mixed relatively fresh suspended sediment
transported down the rivers with suspended sediments in estuary waters. Segregation of the samples into groups with similar
degrees of mixing between river and estuary water revealed that transport of suspended sediments from the Sacramento-San Joaquin
drainage basin strongly influenced the concentration and distribution of sediment-associated pesticides entering the San Francisco
Bay. The less-mixed suspended sediment contained a different distribution of pesticides than the sediments exposed to greater
mixing. Temporal trends were evident in pesticide content after samples were segregated according to mixing history. These
results indicate sampling strategies that collect at a low frequency or do not compare samples with similar mixing histories
will not elucidate basin processes. Despite the considerable influence of mixing, a large number of pesticides were found
associated with the suspended sediments. Few pesticides were found in the concurrent water samples and in concentrations much
lower than predicted from equilibrium partitioning between the aqueous and sedimentary phases. The observed sediment-associated
pesticide concentrations may reflect disequilibria between sedimentary and aqueous phases resulting from long equilibration
times at locations where pesticides were applied, and relatively short transit times over which re-equilibration may occur.