A Comparative Analysis of Eutrophication Patterns in a Temperate Coastal Lagoon
The coastal bays and lagoons of Maryland extend the full length of the state's Atlantic coast and compose a substantial ecosystem
at the land-sea margin that is characterized by shallow depth, a well-mixed water column, slow exchange with the coastal ocean,
and minimal freshwater input from the land. For at least 25 years, various types of measurements have been made intermittently
in these systems, but almost no effort has been made to determine if water quality or habitat conditions have changed over
the years or if distinctive spatial gradients in these features have developed in response to changing land uses. The purpose
of this work was to examine this fragmented database and determine if such patterns have emerged and how they may be related
to land uses. Turbidity, dissolved inorganic phosphate, algal biomass, and primary production rates in most areas of the coastal
bays followed a regular seasonal pattern, which was well correlated with water temperature. Nitrate concentrations were low
(<5 μM), and only modestly higher in tributary creeks (<20 μM). Additionally, there was little indication of the spring bloom
typical of river-dominated systems. There does appear to be a strong spatial gradient in water quality conditions (more eutrophic
in the upper bays, especially in tributary creeks). Comparisons of water quality data collected between 1970 and 1991 indicate
little temporal change in most areas and some small improvements in a few areas, probably related to decreases in point-source
discharges. Seagrass communities were once extensive in these systems but at present are restricted to the eastern portion
of the lower bays where water clarity is sufficient to support plant survival. Even in these areas, seagrass densities have
recently decreased. Examination of diel dissolved oxygen data collected in the summer indicates progressively larger diel
excursions from lower to upper bays and from open bays to tributary subsystems; however, hypoxic conditions (<2 mg 1−1) were rarely observed in any location. Nitrogen input data (point, surface runoff, groundwater and atmospheric deposition
to surface waters) were assembled for seven regions of the coastal bay system; annual loading rates ranged from 2.4 g N m−2 yr−1 to 39.7 g N m−2 yr−1. Compared with a sampling of loading rates to other coastal systems, those to the upper and lower bays were low while those
to tributaries were moderate to high. Regression analysis indicated significant relationships between annual nitrogen loading
rates and average annual total nitrogen and chlorophyll a concentrations in the water column. Similar analyses also indicated significant relationships between chlorophyll a and the magnitude of diel dissolved oxygen changes in the water column. It is concluded that these simple models, which could
be improved with a well-designed monitoring program, could be used as quantitative management tools to relate habitat conditions
to nutrient loading rates.
Available from: Shuiwang Duan
- "Concentrations of dissolved nitrogen species and their spatiotemporal variability in the MCBs have been investigated in previous studies (Boynton et al., 1996; Glibert et al., 2007, 2014). Results of Boynton et al. (1996) showed very low concentrations of nitrate and nitrite (<1.0 mM) and ammonium (1e4 mM). "
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ABSTRACT: Dissolved organic matter (DOM) provides nutrients and energy subsidies for harmful algal blooms in Maryland's Coastal Bays (MCBs, USA). The composition, sources and dynamics of DOM in MCBs are not well known. In this study, dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were monitored monthly over a period of one year (July 2011 to June 2012) at 13 stations in the MCBs. Absorption and fluorescence spectroscopy were used to characterize DOM composition and track terrestrial inputs versus aquatic sources of DOM. Results show that DOC and TDN concentrations in the MCBs (187–501 μM and 19.4–40.6 μM) were comparable to eutrophic coastal waters in the United States but much higher than the mid-Atlantic Bight. This suggests that the MCBs are a DOM source for the coastal ocean. Spatially, nearshore sites had relatively higher DOC and TDN concentrations and terrestrially-derived aromatic DOM (indicated by high humification index) than the bays that were directly connected to the Atlantic Ocean. Seasonally, DOC from the main body of the MCBs (Chincoteague and Assawoman Bays) displayed a pronounced seasonal pattern with the highest values occurring in summer. Protein-like DOM from algal/bacterial inputs (indicated by high biological freshness index or fluorescence index) was also highest in summer but then decreased gradually until April. DOC concentrations at the nearshore site were highest in later spring, probably due to terrestrial inputs. Conversely, TDN concentrations in smaller bays with faster flushing rates (Newport, Sinepuxent and Isle of Wight Bays) were highest in April, probably due to watershed nitrogen inputs. This spring TDN peak was not apparent in the main body of the MCBs, which have longer flushing times (indicating stronger biological nitrogen uptake). This study suggests that DOM in eutrophic, shallow coastal bays such as the MCBs consists of a large fraction of protein-like components from local algal/microbial sources during summer. This enhanced primary productivity is likely fueled by watershed nitrogen inputs from agricultural and urban land use during spring. Further insights regarding spatiotemporal variations and controls of DOM abundance, composition and sources in the MCBs can be helpful in guiding and prioritizing coastal restoration efforts for reducing eutrophication and water quality degradation.
- "Coastal lagoons are often very shallow, productive, bordered by human development, and have long residence times, which raise the concern over future eutrophication through climate change (Lloret et al., 2008). Although eutrophication based impacts have been historically observed by Nixon (1995) in systems such as Moriches Bay in Long Island, New York, other coastal lagoons are often oligotrophic despite increased loadings over time (Boynton et al., 1996; Lloret et al., 2008). Estuaries are also prone to pulsed nutrient supply and rapidly changing nutrient dynamics that influences phytoplankton community biomass and structure in short timeframes (Pinckney et al., 1999). "
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ABSTRACT: Weekly inorganic nutrient and chlorophyll-a concentrations were measured to establish baseline conditions in Corpus Christi Bay, Texas during seasonal hypoxia and harmful algal bloom (HAB) formation. Two fixed stations along the southern shoreline were sampled weekly for a continuous year at the same time each day. Weekly shoreline observations were found to be statistically similar to quarterly observations in the bay center, but with a greater power to detect seasonal trends. Dissolved Oxygen (DO)<4mg/L was measured in June, 2012 along the southern shoreline of Corpus Christi Bay, which places lower DO conditions west of previous estimates. During a bay-wide HAB event in November of 2011 no changes were observed in any of the nutrient or chlorophyll-a observations. This study documents a baseline of nutrients and chlorophyll-a in Corpus Christi Bay during a dry (average salinity>36PSU) year.
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Available from: Shailesh Kumar Patidar
- "Among the nutrients from anthropogenic sources, phosphorus (P) and nitrogen (N) are of major concern in eutrophication    . The environmental parameters of water and biomass productivity are correlated and have a regular seasonal pattern along coastal bays . Some metals like Cu, Ni, Bo, Zn, Mg, Mn, Mo, Co, Fe, and Ca are important, which trigger the growth of microalgae up to a certain limit. "
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ABSTRACT: The objective of this study is to understand the fatty acid composition of a naturally floating microalgal mat with respect to seasonal variations in the water of a eutrophic lagoon on the west coast of India. The floating microalgal mat was explored for its bioaccumulation of metals and lipids for sustainable utilization in biofuel production. The effects of the nutrient profile and heavy metals in the water on the community composition of microalgal mat in different seasons were also studied and a principal component analysis was performed. It was observed that the unsaturated fatty acids such as C18:1n9c and C18:2n6c increased in low temperatures. The reverse effect was observed during the pre-monsoon season with augmented C16:0 fatty acid and an overall increment in saturated fatty acids. The Cyanophyceae and diatom community nurtured the growth during the pre-monsoon season by acquiring a higher bioaccumulation concentration factor (BCF) for Mn (3812.6 ± 680), As (90.47 ± 15.38), Ni (1620 ± 163.64), Cr (73.27 ± 21.23), and Cu (46.40 ± 11.44). The higher abundance of Cyanophyceae in the microalgal mat exhibited better metal endurance during the pre-monsoon season, which could be obviously utilized for the bioremediation of heavy metals. The biodiesel prepared from the microalgal mat met European biodiesel standards.
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