Bay Water Quality Research Articles

Groundwater and surface water quality in a coastal bay with negligible fresh groundwater discharge: Arraial do Cabo, Brazil

Submarine groundwater discharge (SGD) is an important mechanism governing the flux of materials to the coastal region. The loading of nutrients to coastal regions occurs through terrestrial outflow, atmospheric deposition and exchanges with the ocean. In this study, multiple tracers of groundwater input (223Ra, 224Ra, 226Ra, 228Ra, salinity, Ba, Si, U, δ(18O) and δ(2H)) were used to determine the amount of nutrients contributing to the submarine groundwater discharge in the Arraial do Cabo region, which is located on Brazil's southeastern coast. This region is a summer resort, and its population increases by a factor of ten during vacation periods. The nutrient concentrations peaked at 1700μmolL−1 for NO3− and 900μmolL−1 for NH4+ in groundwater wells close to the beachfront; however, no elevated nutrient concentrations were observed in the coastal seawater. This finding was credited to the existence of a physical barrier which hinders the existence of freshwater SGD and also due to the groundwater pumping existent on almost all buildings close to the shoreline. Seepage experiments demonstrated the presence of SGD, which represents recirculated seawater, based on the δ(18O) and δ(2H) levels and is about 0.06m3m−2day−1. Ra was enriched in groundwater samples (1.2±1.0Bqm−3 for 223Ra and 12.2±9.2Bqm−3 for 224Ra, 95% confidence interval) compared to seawater samples (0.077±0.013Bqm−3 for 223Ra and 0.66±0.17Bqm−3 for 224Ra, 95% confidence interval).

東北太平洋沖地震津波後の大船渡湾の水質・底質の現状

東北太平洋沖地震津波後の大船渡湾の水質・底質の現状

4次元変分法による流速鉛直分布のデータ同化

Four dimensional variational (4D-Var) data assimilation is carried out using Regional Ocean Modeling System (ROMS) and the vertical current profiles which are measured by Osaka Bay Water Quality Observation System in this paper. The applicability of 4D-Var is tested through the sensitivity analyses in which parameters for 4D-Var and sets of control variables are changed. The RMSE of velocity at the observation stations decreases more with the number of inner-loop of 10, the radii of horizontal and vertical error covariance of 5 km and 3m respectively. The effect of the 4D-Var appears in the analyses of velocity near the surface at some stations where there is larger difference from the observations and those of surface salinity even though salinity is not assimilated directly.

Water properties in Chesapeake Bay from MODIS-Aqua measurements

This study evaluates the performance of ocean color products derived from measurements of the Moderate Resolution Imaging Spectroradiometer (MODIS) on the satellite Aqua using the standard near-infrared (NIR) and the shortwave infrared (SWIR)-based atmospheric correction algorithms in the Chesapeake Bay. The MODIS-Aqua-derived normalized water-leaving radiances, nLw(λ), and chlorophyll-a (Chl-a) data are compared with in situ radiometric measurements from the NASA SeaWiFS Bio-optical Archive and Storage System (SeaBASS) database and Chl-a data from the Chesapeake Bay Water Quality Database. Results show that, using the NIR-SWIR combined ocean color data processing, improved nLw(λ) and Chl-a data products can be produced in the Chesapeake Bay. However, Chl-a data are still overestimated in some Chesapeake Bay regions, in particular, in the upper bay region where waters are strongly influenced by the total suspended sediment (TSS) concentration. Specifically, using the NIR-SWIR approach, mean ratios of MODIS-derived and in situ-measured nLw(λ) at wavelengths of 412, 443, 488, 531, 551, and 667nm for the Chesapeake Bay are 1.288, 1.093, 0.998, 0.946, 0.908, and 0.865, respectively, while mean Chl-a values over the region from satellite-derived and in situ-measure data are 11.14 and 10.28mg·m−3, respectively. Based on a strong correlation relationship between TSS and water diffuse attenuation coefficient, a regional TSS algorithm for the Chesapeake Bay has been developed and validated, with mean ratio of 1.064 between MODIS-derived and in situ-measured TSS data. Therefore, using the NIR-SWIR algorithm for MODIS-Aqua ocean color data processing, nLw(λ), Chl-a, and TSS data from 2002 to 2010 for the Chesapeake Bay have been generated and used for characterizing the water properties in the region, showing strong seasonal and interannual variability, as well as important spatial variations in the region.

Pennsylvania’s Nutrient Trading Program

The Chesapeake Bay and its tidal waters are listed as impaired under the Clean Water Act (CWA) due to high amounts of nitrogen, phosphorous, and sediment, which in excess can create algae blooms that consume oxygen vital to fish and shellfish, block sunlight for underwater Bay vegetation, and smother bottom dwelling aquatic life. These nutrients and sediments enter the water from agricultural operations, storm water runoff, wastewater facilities, air pollution and other sources. Under the CWA, jurisdictions that have waterways designated as impaired must create a TMDL, which is essentially a “pollution diet” that identifies the maximum amount of a pollutant the waterway can receive, and still meet United States Environmental Protection Agency (EPA) water quality standards. For more than twenty-five years there have been considerable voluntary efforts by states within the Chesapeake Bay watershed to address the amount of nutrients and sediments entering the Bay, with the goal of removing the Bay from the CWA’s list of impaired waters. However, these efforts did not result in the Bay’s removal from the list, and on December 29, 2010, EPA announced a TMDL for the entire Chesapeake Bay watershed. For the Bay TMDL, EPA required Bay jurisdictions to detail how they would meet their respective nutrient allocations through a Watershed Implementation Plans (WIP). The WIP provides a roadmap for how each Bay jurisdiction, in partnership with federal and local governments, will achieve and maintain the Bay TMDL nitrogen, phosphorous, and sediment allocations necessary to meet Bay water quality standards. Pennsylvania’s WIP includes the Nutrient Credit Trading (NCT) Program.

Simulating the effect of hypoxia on bay anchovy egg and larval mortality using coupled watershed, water quality, and individual-based predation models

Greater nutrient loads since the 1950s have increased the extent and duration of hypoxic conditions in the Patuxent River and the Chesapeake Bay (Maryland, USA). We linked watershed, water quality, and individual-based predation models to predict how changes in local (Patuxent River watershed) and regional (bay-wide) nutrient loading rates would affect bay anchovy Anchoa mitchilli egg and larval mortality rates in the lower region of the Patuxent River. Nutrient loadings affected hypoxic volume and the degree of spatial overlap between anchovy and their predators. Mortality rates were simulated during June and July under combinations of a wet or dry year, reduced and increased nutrient loadings from the Patuxent River watershed, and increased and decreased nutrient loadings into the Patuxent River at the Chesapeake Bay boundary. Chesapeake Bay water quality at the downstream boundary had a much larger effect on egg and larval mortality rates than nutrient loading rates from the Patuxent River watershed, and these responses were consistent with the downstream boundary condition having a greater effect on hypoxia. Water column structure, year type (wet/dry), and location within the lower Patuxent River had smaller effects on egg and larval mortality. Due to indirect effects, the effect of the Chesapeake Bay boundary condition on larval mortality rates during June was opposite to that predicted for egg mortality rates. Our results illustrate that statements and justifications about the benefits of nutrient loading reductions on estuarine ecosystems should avoid oversimplification, be specific, and recognize that species responses to changes in environmental conditions can be complex and variable.

Multiple stressor effects on water quality in Poplar Bay, Lake of the Woods, Canada: a midge-based assessment of hypolimnetic oxygen conditions over the last two centuries

Chironomid and Chaoborus (midge) remains preserved in a dated sediment core from Poplar Bay, Lake of the Woods (LOW), Ontario, Canada, were used to assess the effects of multiple stressors (e.g., recent warming and shoreline development) on water quality over the past ~200 years. As monitoring data for LOW do not extend beyond recent decades, paleolimnological methods are used to reconstruct long-term limnological trends and to establish pre-disturbance conditions. The effects of recent warming and shoreline development on Poplar Bay water quality are examined using an index of hypolimnetic oxygen (O2) status based on the ratio of Chaoborus to chironomid remains (chaob:chir) and a midge-inferred volume-weighted hypolimnetic oxygen (VWHO) model. Our paleolimnological data indicate that hypolimnetic [O2] in Poplar Bay have been historically hypoxic (1-4 mg O2 L-1) but have declined further (generally <2 mg O2 L-1) over the last few decades. Significant relationships between air temperature and midge data indicate that substantial warming starting in the late-1970s has triggered a marked response in the midge assemblages that pre-dates the onset of cottage development (mid-1990s). These findings complement a diatom-based study on the same sediment core, likewise suggesting that recent warming has played a prominent role in structuring limnetic communities. However, it is likely that the full, compounded effects of recent warming and shoreline development have not yet been realized. Our study highlights the complexity of multiple stressor systems, such as Poplar Bay, and emphasizes the benefits of using multiple, independent lines of paleoenvironmental evidence in gaining a more complete understanding of historical water quality.

Landowner willingness to implement riparian buffers in a transitioning watershed

The Chesapeake Bay watershed of the northeastern U.S. has experienced extensive transition from agricultural to residential land uses. However, riparian buffer implementation research has generally focused on agricultural land uses and participation in agricultural conservation programs. Our research examines landowner willingness to implement riparian buffers in the Spring Creek watershed of central Pennsylvania, a sub-watershed of the Chesapeake Bay basin, which has also undergone population growth and land use transition. We conducted a mail survey of riparian residential, small agricultural, and agricultural landowners (n=175) to assess attitudes toward buffer implementation. Our results indicated that residential riparian respondents were 94% less willing than agricultural riparian respondents to implement a buffer on their property, net of other factors. Neighborhood friendships positively predicted willingness to implement buffers and also increased implementation willingness under certain incentive scenarios. Our findings indicate that landowners will become more willing to implement riparian buffers if they believe these buffers will have positive outcomes. Knowledge of Chesapeake Bay water quality, a central cause for riparian conservation programs, did not predict implementation willingness. As landscapes continue to transition toward residential uses, it is imperative that conservation programs adapt buffer design and program incentives to meet riparian residential landowner normative and aesthetic preferences.

Effect of HCH on the Jiaozhou Bay Waters-the Transfer Laws of HCH

Abstract By investigation data in Jiaozhou bay waters from 1979 to 1986(absent of 1980), in spacial scale, by the analysis of the annual dataset, from the view of the content, and the horizontal, vertical and seasonal distributions of HCH, the study of the source, water quality, distribution and transfer state in Jiaozhou bay showed many results of the HCH transfer laws. In temporal scale, by the analysis of the five-year dataset from 1979 to 1986(absent of 1980), the study of the variation process of HCH in Jiaozhou bay showed the below results: the annual variation of the content, the change process of the source, the land transfer process, the water transfer process and the sedimentary process. These laws and process variations provided the solid theoretical base for the HCH transfer in the water body and edified for the study of the other organic compound transfer in the water body.

Effects of land-based pollution control on coastal hypoxia: a numerical case study of integrated coastal area and river basin management in Ise Bay, Japan

Abstract Integrated Coastal Area and River basin Management (ICARM) is important to maintain/improve the sustainability of the coastal ecosystem services. We describe the effects of the land-based pollution reduction on the water quality in Ise Bay, Japan, based on the numerical simulations. The numerical model for water and material flow-flux in the bay consists of the hydrodynamic and the pelagic-benthic ecosystem models. The hydrodynamic model could predict the 3D current, pressure, salinity, and temperature. The pelagic-benthic ecosystem model simulated the available evaluation for the C-N-P-O biogeochemical cycle. The numerical simulations were carried out in order to investigate the response of coastal hypoxia in Ise Bay to the pollutant loading reductions predicted by the river basin model under the various social scenarios. These simulated results indicated that hypoxia volume could be reduced to 67% of the present loading condition if the most effective control of the point and nonpoint sources was adopted

大阪湾再生水質一斉調査結果から見た大阪湾の水質分布について

大阪湾再生水質一斉調査結果から見た大阪湾の水質分布について

Long-Term Trends in Chesapeake Bay Seasonal Hypoxia, Stratification, and Nutrient Loading

A previously observed shift in the relationship between Chesapeake Bay hypoxia and nitrogen loading has pressing implications on the efficacy of nutrient management. Detailed temporal analyses of long-term hypoxia, nitrogen loads, and stratification were conducted to reveal different within-summer trends and understand more clearly the relative role of physical conditions. Evaluation of a 60-year record of hypoxic volumes demonstrated significant increases in early summer hypoxia, but a slight decrease in late summer hypoxia. The early summer hypoxia trend is related to an increase in Bay stratification strength during June from 1985 to 2009, while the late summer hypoxia trend matches the recently decreasing nitrogen loads. Additional results show how the duration of summertime hypoxia is significantly related to nitrogen loading, and how large-scale climatic forces may be responsible for the early summer increases. Thus, despite intra-summer differences in primary controls on hypoxia, continuing nutrient reduction remains critically important for achieving improvements in Bay water quality.

Simulated Short‐Term Impacts of the Atlantic Menhaden Reduction Fishery on Chesapeake Bay Water Quality

AbstractAtlantic menhaden Brevoortia tyrannus support an intense fishery in Chesapeake Bay, an estuary that is impaired by eutrophication and excess phytoplankton biomass. Since Atlantic menhaden are filter‐feeding fish that consume plankton, including phytoplankton, fishery removals may negatively affect water quality and may therefore hinder bay restoration efforts. We performed a simulation to estimate the short‐term (monthly and annual) water quality impacts caused by the reduction fishery harvesting its current total allowable catch of Atlantic menhaden in Chesapeake Bay (109,020 metric tons/year). A theoretical loss in net nitrogen removal (Nt) due to the fishery was estimated for each month, and the simulation was repeated for several scenarios to account for uncertainties associated with Atlantic menhaden feeding behavior. The largest potential impact of the fishery (i.e., absolute value of Nt) occurred in August for all scenarios, but depending on the value assumed for average feeding rate the fishery was estimated to have either a positive impact or a negative impact on water quality. The sum of Nt across months ranged from −5.78 × 105 to 1.85 × 107 kg of N/year, indicating that the harvested Atlantic menhaden could have contributed up to 0.38% or removed up to 12.19% of the estimated total nitrogen load for Chesapeake Bay. This large range probably captures all possible scenarios of Atlantic menhaden feeding intensity; however, the current understanding of their feeding rates as related to phytoplankton composition in Chesapeake Bay suggests that average feeding rates are relatively low and that the probable impact of the fishery on water quality is negligible.Received July 13, 2010; accepted December 24, 2010

Chemometry use in the evaluation of the sanya bay water quality

In this study, chemometric method is employed to identify anthropogenic effects on the water quality in Sanya Bay, South China Sea, and its marine and natural characteristics. Principal component analysis has extracted the four latent factors, thus explaining 85.52% of the total variance. Cluster analysis and principal component analysis have identified three different patterns of water quality based on anthropogenic effects and marine characteristics: Cluster I located in the outer and middle parts of the bay, Cluster II close to downtown Sanya, Cluster III located in the Sanya River estuary. In terms of the temporal pattern, principal component analysis and cluster analysis have distinguished the dry season from November to the following April, and the rainy season from May to October. The temporal pattern is related to climate and natural characteristics. The similarity index between variables and scores of samples can further distinguish the contribution of the variables to the samples. Both the polluting sources external to the Sanya River and the water from the South China Sea exercise an important influence on the water quality in Sanya Bay. These results may be valuable for socioeconomic development and human health in the Sanya Bay area.

Biocalcification in the Eastern Oyster (Crassostrea virginica) in Relation to Long-term Trends in Chesapeake Bay pH

Anthropogenic carbon dioxide (CO2) emissions reduce pH of marine waters due to the absorption of atmospheric CO2 and formation of carbonic acid. Estuarine waters are more susceptible to acidification because they are subject to multiple acid sources and are less buffered than marine waters. Consequently, estuarine shell forming species may experience acidification sooner than marine species although the tolerance of estuarine calcifiers to pH changes is poorly understood. We analyzed 23 years of Chesapeake Bay water quality monitoring data and found that daytime average pH significantly decreased across polyhaline waters although pH has not significantly changed across mesohaline waters. In some tributaries that once supported large oyster populations, pH is increasing. Current average conditions within some tributaries however correspond to values that we found in laboratory studies to reduce oyster biocalcification rates or resulted in net shell dissolution. Calcification rates of juvenile eastern oysters, Crassostrea virginica, were measured in laboratory studies in a three-way factorial design with 3 pH levels, two salinities, and two temperatures. Biocalcification declined significantly with a reduction of ∼0.5 pH units and higher temperature and salinity mitigated the decrease in biocalcification.

Towards carrying capacity assessment for aquaculture in the Bolinao Bay, Philippines: A numerical study of tidal circulation

The increase in intensive aquaculture production in the Bolinao Bay, Philippines reached the point of harmful influence to production stock. Up to the present, there has been no estimation of aquaculture carrying capacity which is based on quantification of processes responsible for (a) water quality inside the units, (b) impact to the seabed and (c) water quality in the whole Bolinao Bay. The numerical estimation of tidal circulation, which is the most dominant part of the hydrodynamical regime in the Bolinao Bay, represents an unavoidable step in the carrying capacity determination considering points (a), (b) and (c). The hydrodynamical model we apply is a free surface, 3D finite element tidal model, forced with sea elevation dynamics at three open boundaries. It incorporates an increase in bottom stress drag coefficients in the coral areas and advanced transport corrected advection scheme. The model simulations of water flow show good agreement with measured currents in the central part of the Bolinao Bay, southern and northeastern channel, while agreement in the areas in vicinity of northern channel is not as tight. In order to provide an insight into the water exchange in aquaculture units, to support local water quality models and seabed deposition models (points (a) and (b)), the area is mapped with neap tide mean, spring tide mean and 14-day mean current velocity contours. The highest 14-day mean velocities are attained in the southern channel (>17 cm s −1), while the mean velocities characteristic for northern part (<6 cm s −1) and shallow areas of coral reefs (<2 cm s −1) are much lower. Area-mean difference between spring tide and 14-day mean velocities is estimated to be 18.32% ( std = 7.31 % ), while difference between neap tide and 14-day mean velocities is 17.62 % ( std = 11.19 %). To support global basin-wide water quality models (point (c)), retention of water in the bay is estimated by Lagrangian and Eulerian calculation procedure of mean residence time field. Both calculations estimate the highest (no-wind) residence times (Lan: 25.4 days, Eul: 21.03 days) in the central northern part, but most of the area (Lan: 73.11%, Eul: 79.31%) is characterized by residence time values significantly lower than 15 days. The results are readily applicable for upcoming implementation in the models of local (aquaculture units, seabed) and basin-wide (Bolinao Bay) nutrient dynamics, primary and secondary production, organic matter decomposition and oxygen dynamics.

Evaluation of sediment profile imagery as a tool for assessing water quality in Greenwich Bay, Rhode Island, USA

Abstract The Benthic Habitat Quality (BHQ) index was used to assess habitat visible in sediment profile images (SPI) following hypoxia disturbance in a shallow ( −1 , 2.9 mg l −1 , and 4.8 mg l −1 ). Using categorical data analysis, we established empirical relationships between hypoxia prevalence and presence/absence of biogenic features visible in SPI. Fecal pellets, tubes, feeding pits, voids, mounds, and BHQ score were good affirmative features, meaning that their presence (or score greater than 5) indicated a high probability of good water quality. However, low sensitivity to hypoxia precluded their usefulness as indicators, and was attributed to rarity in images and to factors acting on time intervals longer than those examined, e.g. long-term organic enrichment or hypoxia. Burrow structures and the apparent redox potential discontinuity (aRPD), or oxidized layer of surface sediment, were good discriminatory features, with high sensitivity and specificity for both hypoxia and normoxia. Both were strong surrogates for water quality over multiple assessment windows and DO thresholds, and had the highest overall predictive values. We conclude that SPI images can be used to widen the spatial extent of water quality monitoring efforts by utilizing the relationships between aRPD, burrows and hypoxia prevalence.

Study of the Characteristics of Flow Structure and Water Quality in IMARI Bay by means of Field Observation and Numerical Model

Recently, an increase in the load from the land and a food scatter of aquaculture causes eutrophication in IMARI Bay. Therefore, red tides have been generated. It is necessary to decrease the red tide. So, as a basic research, we clarify the characteristics of flow structure and water quality by means of field observations and a numerical model. As a consequence, it is clear that flow structure around bay mouth is very complex. Bay water flows out in the upper layer during ebb tide, and outer sea water flows into the lower layer during flood tide. It is realized that the tidal exchange is strong comparatively in the western part of the bay, while it is weak in the central and south-eastern part.

The Relative Importance of Road Density and Physical Watershed Features in Determining Coastal Marsh Water Quality in Georgian Bay

We used a GIS-based approach to examine the influence of road density and physical watershed features (watershed size, wetland cover, and bedrock type) on water quality in coastal marshes of Georgian Bay, Ontario. We created a GIS that included landscape information and water-quality data from a 9-year synoptic survey of 105 coastal marshes covering 28 quaternary watersheds. Multiple regressions and partial correlations were used to discern confounding effects of human-induced (road density) versus natural physical watershed determinants of water quality. Road density was the dominant factor influencing many water quality variables, showing positive correlations with specific conductivity (COND), total suspended solids (TSS), and inorganic suspended solids (ISS) and a negative correlation with overall Water Quality Index scores. Road density also showed positive correlations with total nitrate nitrogen (TNN) and total phosphorus (TP). By comparison, larger watershed area was the main factor leading to elevated TP concentrations. The proportion of the watershed occupied by wetlands explained the largest amount of variation in TNN concentrations (negative correlation) and was also negatively correlated with COND and positively correlated with TSS and ISS when we controlled for road density. Bedrock type did not have a significant effect in any of the models. Our findings suggest that road density is currently the overriding factor governing water quality of coastal marshes in Georgian Bay during the summer low-flow period. We recommend that natural variation in physical watershed characteristics be considered when developing water quality standards and management practices for freshwater coastal areas.

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

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