Shallow Coastal Bays Research Articles

Mid-Carboniferous diversification of continental ecosystems inferred from trace fossil suites in the Tynemouth Creek Formation of New Brunswick, Canada

We report Skolithos, Scoyenia and Mermia Ichnofacies from sub-humid tropical fluvial megafan deposits in the Lower Pennsylvanian Tynemouth Creek Formation of New Brunswick, Canada, and discuss their evolutionary and palaeoecological implications, especially regarding the colonization of continental freshwater/terrestrial environments. The Skolithos Ichnofacies comprises annelid/arthropod spreite in the upper storey of a fluvial channel. The Scoyenia Ichnofacies comprises tetrapod tracks, arthropleurid trackways, and shallow annelid/arthropod burrows in active/abandoned fluvial channels and rapidly aggrading levees/splays in proximal interfluve areas. The Mermia Ichnofacies comprises abundant xiphosuran trackways, along with diverse traces of other arthropods, annelids, mollusks, and fish, in shallow freshwater lakes, ponds, and coastal bays in slowly aggrading distal interfluve areas. Transitional Mermia/Scoyenia Ichnofacies comprise tetrapod, mollusk and annelid/arthropod traces in coastal bay deposits on the distal edge of the megafan. These trace fossil suites (1) provide the clearest documentation yet of the mid-Carboniferous diversification event, when tropical continental environments became more densely populated; (2) suggest that euryhaline visitors (xiphosurans, microconchids, and other taxa) from open marine settings played a key role in this episode of freshwater colonization; and (3) provide empirical support for the “Déjà vu Effect”, the evolutionary concept that new or empty ecospace, recurrent in spatially and temporally variable environments, is colonized by simple ichnocoenoses.

Dynamics of dissolved organic carbon and total dissolved nitrogen in Maryland's coastal bays

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.

Seagrass metabolism across a productivity gradient using the eddy covariance, Eulerian control volume, and biomass addition techniques

AbstractThe net ecosystem metabolism of the seagrass Thalassia testudinum was studied across a nutrient and productivity gradient in Florida Bay, Florida, using the Eulerian control volume, eddy covariance, and biomass addition techniques. In situ oxygen fluxes were determined by a triangular Eulerian control volume with sides 250 m long and by eddy covariance instrumentation at its center. The biomass addition technique evaluated the aboveground seagrass productivity through the net biomass added. The spatial and temporal resolutions, accuracies, and applicability of each method were compared. The eddy covariance technique better resolved the short‐term flux rates and the productivity gradient across the bay, which was consistent with the long‐term measurements from the biomass addition technique. The net primary production rates from the biomass addition technique, which were expected to show greater autotrophy due to the exclusion of sediment metabolism and belowground production, were 71, 53, and 30 mmol carbon m−2 d−1 at 3 sites across the bay. The net ecosystem metabolism was 35, 25, and 11 mmol oxygen m−2 d−1 from the eddy covariance technique and 10, −103, and 14 mmol oxygen m−2 d−1 from the Eulerian control volume across the same sites, respectively. The low‐flow conditions in the shallow bays allowed for periodic stratification and long residence times within the Eulerian control volume that likely reduced its precision. Overall, the eddy covariance technique had the highest temporal resolution while producing accurate long‐term flux rates that surpassed the capabilities of the biomass addition and Eulerian control volume techniques in these shallow coastal bays.

Controls on residence time and exchange in a system of shallow coastal bays

Patterns of transport and residence time influence the morphology, ecology and biogeochemistry of shallow coastal bay systems in important ways. To better understand the factors controlling residence time and exchange in coastal bays, a three-dimensional finite-volume coastal ocean model was set up and validated with field observations of circulation in a system of 14 shallow coastal bays on the Atlantic coast of the USA (Virginia Coast Reserve). Residence times of neutrally buoyant particles as well as exchange among the bays in the system and between the bays and the ocean were examined with Lagrangian particle tracking. There was orders of magnitude variation in the calculated residence time within most of the bays, ranging from hours in the tidally refreshed (repletion) water near the inlets to days–weeks in the remaining (residual) water away from the inlets. Residence time in the repletion waters was most sensitive to the tidal phase (low vs. high) when particles were released whereas residence time in the residual waters was more sensitive to wind forcing. Wind forcing was found to act as a diffuser that shortens particle residence within the bays; its effect was higher away from the inlets and in relatively confined bays. Median residence time in the bays significantly decreased with an increase in the ratio between open water area and total area (open water plus marsh). Exchange among the bays and capture areas of inlets (i.e., exchange between the bays and the ocean) varied considerably but were insensitive to tidal phase of release, wind, and forcing conditions in different years, in contrast to the sensitivity of residence time to these factors. We defined a new quantity, termed shortest-path residence time, calculated as distance from the closest inlet divided by root-mean-square velocity at each point in model domain. A relationship between shortest-path residence time and particle-tracking residence time provides a means of estimating residence time over an entire model domain.

Benthic megafauna and CO2 bubble dynamics observed by underwater photography during a controlled sub-seabed release of CO2

In 2012, a controlled sub-seabed release of carbon dioxide (CO2) was conducted in Ardmucknish Bay, a shallow (12m) coastal bay on the west coast of Scotland. During the experiment, CO2 gas was released 12m below the seabed for 37 days, causing significant disruption to sediment and water carbonate chemistry as the gas passed up through the sediment and into the overlying water. One of the aims of the study was to investigate how the impacts caused by leakage from geological CO2 Capture and Storage (CCS) could be detected and quantified in the context of natural heterogeneity and dynamics. To do this underwater photography was used to analyze (i) the benthic megafaunal response to the CO2 release and (ii) the dynamics of the CO2 bubble streams, emerging from the seabed into the overlying water column. The frequently observed megafauna species in the study area were Virgularia mirabilis (Cnidaria), Turritella communis (Mollusca), Asterias rubens (Echinodermata), Pagurus bernhardus (Crustacea), Liocarcinus depurator (Crustacea), and Gadus morhua (Osteichthyes). No discernable abnormal behavior was observed for these megafauna, in any of the zones investigated, during or after the CO2 release. Time-lapse photography revealed that the intensity and presence of the CO2 bubble plume was affected by the tides, with the most active bubbling seen at low tides and the larger hydrostatic pressure at high tide suppressing CO2 bubbling from the seabed.

In Situ Hatching Success of Calanoid Copepod Eggs in Hypoxic Sediments of a Coastal Bay

ABSTRACT Choi, K-H.; Jang, M-C.; Shin, H.H.; Lee, W-J., and Shin, K., 2016. In situ hatching success of calanoid copepod eggs in hypoxic sediments of a coastal bay. Hypoxia can have adverse effects on recruitment of marine copepods via its effects on egg hatching and survival of nauplii. This study investigated the effects of hypoxia on in situ hatching success of calanoid copepods in Gamak Bay, Korea, a shallow (9-m) microtidal coastal bay with long water residence times exceeding a month. Plankton emergence trap/chambers were placed into seafloor–surface sediments in July at a hypoxic site (mean = 0.6 mL L−1) in the inner part of the bay and at a normoxic site in the mid bay. Nauplii that hatched and left the sediment were collected daily for 12 days, and the top 1 cm of sediment was preserved at the end of incubation. The number of eggs in the sediment was >3 × 105 eggs m−2 at the hypoxic site, about six times that at the normoxic site. Most of the eggs appeared to be subitaneous. Egg-hatching rate in ...

Impact of river discharge, upwelling and vertical mixing on the nutrient loading and productivity of the Canadian Beaufort Shelf

Abstract. The concentrations and elemental stoichiometry of particulate and dissolved pools of carbon (C), nitrogen (N), phosphorus (P) and silicon (Si) on the Canadian Beaufort Shelf during summer 2009 (MALINA program) were assessed and compared with those of surface waters provided by the Mackenzie river as well as by winter mixing and upwelling of upper halocline waters at the shelf break. Neritic surface waters showed a clear enrichment in dissolved and particulate organic carbon (DOC and POC, respectively), nitrate, total particulate nitrogen (TPN) and dissolved organic nitrogen (DON) originating from the river. Silicate as well as bulk DON and DOC declined in a near-conservative manner away from the delta's outlet, whereas nitrate dropped non-conservatively to very low background concentrations inside the brackish zone. By contrast, the excess of soluble reactive P (SRP) present in oceanic waters declined in a non-conservative manner toward the river outlet, where concentrations were very low and consistent with P shortage in the Mackenzie River. These opposite gradients imply that the admixture of Pacific-derived, SRP-rich water is necessary to allow phytoplankton to use river-derived nitrate and to a lesser extent DON. A coarse budget based on concurrent estimates of primary production shows that river N deliveries support a modest fraction of primary production when considering the entire shelf, due to the ability of phytoplankton to thrive in the subsurface chlorophyll maximum beneath the thin, nitrate-depleted river plume. Away from shallow coastal bays, local elevations in the concentration of primary production and dissolved organic constituents were consistent with upwelling at the shelf break. By contrast with shallow winter mixing, nutrient deliveries by North American rivers and upwelling relax surface communities from N limitation and permit a more extant utilization of the excess SRP entering through the Bering Strait. In this context, increased nitrogen supply by rivers and upwelling potentially alters the vertical distribution of the excess P exported into the North Atlantic.

Rates and Forcing of Marsh Edge Erosion in a Shallow Coastal Bay

Salt marshes can experience a significant land loss through erosion and retreat of their perimeter edges. Rates of shoreline change between 1957 and 2007 were determined for four salt marshes in a Virginia coastal bay using aerial photographs and the Digital Shoreline Analysis System (DSAS). High average rates of lateral erosion of 1.0–1.6 m year−1 were found at three marshes, while the edge of the fourth marsh, along the mainland edge of the bay, remained stable. Erosion rates were temporally consistent during the 50-year period at the three eroding sites, although there was a significant spatial variation in rates of change along the length of the edges at these sites. A simple parametric wave model and the SWAN (Simulating WAves Nearshore) spectral wave model were used to calculate incident wave energy flux along the marsh boundaries at each of the sites. Values of wave energy flux agreed fairly well between the two models but are sensitive to the manner in which wave energy flux is calculated. A stronger relationship was found between wave energy flux and volumetric erosion rates along the marsh edges than with lateral erosion rates. This is an important consideration when examining the effects of future sea level rise on marsh loss.

A water movement study in Lianzhou Bay, Guangxi Province, China

This study investigates the physical conditions (water depth, current speed, salinity, temperature) in Lianzhou Bay, a shallow coastal bay in southern China, during two expeditions in the dry and wet seasons of 2011. Based on these expedition data, basic hydrodynamic parameters like Brunt-Vaisala Frequency, Richardson Number, Rossby radius, and Resonance Period are calculated. The results show that Lianzhou Bay is characterized by comparatively small quantity of freshwater input and weak stratification. Strong tides, which are spatially uniform within the bay, cause turbulent mixing. Residence time of the water is shorter in winter due to a stronger coastal current in that season. Consideration of the water movement may help to reduce the harmful ecological impact of aquaculture waste water discharge.

Multidecadal dynamics of larval gobies Pomatoschistus spp. in response to environmental variability in a shallow temperate bay

Compared to commercial fish, there is relatively limited information available about the dynamics of non-commercial fish that very often play important structural and functional roles in marine ecosystems. Long-term investigations that provide quantitative estimates of the population dynamics as a function of environmental variability are needed to understand the ecology and role of the non-commercial fish in the ecosystem, and assist the ecosystem management where relevant. Here we analyze the inter-annual variability and long-term trends of the abundance of the larval non-commercial gobies Pomatoschistus spp. in a shallow coastal bay (Pärnu Bay, northeastern Baltic Sea) in 1959–2010, in relation to climate and prey field related variables. The abundance of larval Pomatoschistus spp. decreased over the last 50 years along with the concomitant decrease in the water transparency. The first appearance of larvae has shifted for about two weeks earlier and is mostly related to the timing of ice cover breakdown. However, some of the effects of the environmental forcing on larval fish may be obscured by the uncertainty of species identification of individuals of the genus Pomatoschistus at larval stage, and the investigated population of Pomatoschistus spp. consists of at least two species with slightly different ecologies and also environmental preferences.

Microphytobenthos and benthic macroalgae determine sediment organic matter composition in shallow photic sediments

Abstract. Microphytobenthos and benthic macroalgae play an important role in system metabolism within shallow coastal bays. However, their independent and interactive influences on sediment organic matter (SOM) are not well understood. We investigated the influence of macroalgae and microphytobenthos on SOM quantity and quality in an experimental mesocosm system using bulk and molecular level (total hydrolyzable amino acids, THAA; phospholipid linked fatty acids, PLFA; pigment) analyses. Our experiment used an incomplete factorial design made up of two factors, each with two levels: (1) light (ambient vs. dark) and (2) macroalgae (presence vs. absence of live macroalgae). Over the course of the 42-day experiment, total organic carbon (TOC) and total nitrogen (TN) increased under ambient light by 173 ± 14 and 141 ± 7%, respectively, compared to in the dark (78 ± 29 and 39 ± 22%). THAA comprised a substantial fraction of SOM (~ 16% of TOC, 35% of TN) and followed TOC and TN accumulation patterns. Mole percent composition of the THAA pool indicated that SOM was composed of more labile organic material (e.g., L-glutamic acid, phenylalanine) under ambient light conditions while SOM in dark treatments was more degraded, with higher proportions of glycine and D-alanine. PLFA content, which represents viable biomass, made up ~ 1% of TOC and contained high levels of algal fatty acids in the light, particularly PLFA derived from diatoms. In the presence of microphytobenthos (i.e., light and macroalgae treatments), SOM lability increased, resulting in the observed increases in bacterial PLFA concentrations. Macroalgae, which were added to half of the light treatments, decreased SOM accumulation compared to light treatments without macroalgae, with TOC and TN increasing by only 130 ± 32 and 94 ± 24%, respectively. This decrease likely resulted from shading by macroalgae, which reduced production of microphytobenthos. The presence of macroalgae decreased SOM lability as well, which resulted in diminished buildup of bacterial biomass. By the final day of the experiment, principal component analysis revealed that sediment composition in treatments with macroalgae was more similar to dark treatments and less similar to light treatments without macroalgae. Overall, microphytobenthos and benthic macroalgae fundamentally altered SOM quality and quantity, which may have notable ecological consequences for shallow-water systems such as increased hypoxia/anoxia, sulfide accumulation, enhanced mineralization and/or stimulated denitrification.

Seasonal Growth and Senescence of a Zostera marina Seagrass Meadow Alters Wave-Dominated Flow and Sediment Suspension Within a Coastal Bay

Tidally driven flows, waves, and suspended sediment concentrations were monitored seasonally within a Zostera marina seagrass (eelgrass) meadow located in a shallow (1–2 m depth) coastal bay. Eelgrass meadows were found to reduce velocities approximately 60 % in the summer and 40 % in the winter compared to an adjacent unvegetated site. Additionally, the seagrass meadow served to dampen wave heights for all seasons except during winter when seagrass meadow development was at a minimum. Although wave heights were attenuated across the meadow, orbital motions caused by waves were able to effectively penetrate through the canopy, inducing wave-enhanced bottom shear stress (τb). Within the seagrass meadow, τb was greater than the critical stress threshold (=0.04 Pa) necessary to induce sediment suspension 80–85 % of the sampling period in the winter and spring, but only 55 % of the time in the summer. At the unvegetated site, τb was above the critical threshold greater than 90 % of the time across all seasons. During low seagrass coverage in the winter, near-bed turbulence levels were enhanced, likely caused by stem–wake interaction with the sparse canopy. Reduction in τb within the seagrass meadow during the summer correlated to a 60 % reduction in suspended sediment concentrations but in winter, suspended sediment was enhanced compared to the unvegetated site. With minimal seagrass coverage, τb and wave statistics were similar to unvegetated regions; however, during high seagrass coverage, sediment stabilization increased light availability for photosynthesis and created a positive feedback for seagrass growth.

Modeling the effects of climate change on eelgrass stability and resilience: future scenarios and leading indicators of collapse

Seagrass meadows influence local hydrodynamics in coastal bays, resulting in a decrease in the shear stress acting on the underlying bed sediment. The reduced sediment suspension and water column turbidity creates a more favorable light environment for further seagrass growth. This positive feedback is strong enough to induce depth-dependent bistable dynamics with 2 possible stable states, an extant meadow and a bare sediment surface. A coupled vegetation-growth hydrodynamic model was used to investigate eelgrass stability and leading indicators of ecosystem shift under the effects of sea-level rise and increases in water temperature associated with climate change. The model was applied to Hog Island Bay, a shallow coastal bay within the Virginia Coast Reserve, USA, where eelgrass restoration efforts are ongoing. The results indicate that while extant eelgrass meadows are likely to tolerate sea-level rise, an increase in the frequency of days when summer water temperature exceeds 30°C will cause more frequent summer die-offs. This increase in the number of higher temperature disturbance events is likely to push a dense meadow initially located within the bistable depth range (1.6 to 1.8 m mean sea level) toward and eventually past a critical bifurcation point, from which recovery is not possible. We identified 2 leading indicators of a meadow nearing this bifurcation point, both associated with the number of leaves per shoot: ‘flickering,’ which reflects conspicuous fluctuations from one attractor to the other across the threshold, and ‘slowing down,’ which is the decreased recovery from perturbations as a system gets close to a threshold. Our model indicates that the eelgrass in these coastal bays has limited resilience to increases in water temperatures predicted from current climate change models.

Wave and tidally driven flows in eelgrass beds and their effect on sediment suspension

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 448:271-287 (2012) - DOI: https://doi.org/10.3354/meps09225 Wave and tidally driven flows in eelgrass beds and their effect on sediment suspension Jennifer C. R. Hansen, Matthew A. Reidenbach* Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA *Email: reidenbach@virginia.edu ABSTRACT: Seagrass beds alter their hydrodynamic environment by inducing drag on the flow, thereby attenuating wave energy and near-bottom currents. This alters the turbulent structure and shear stresses within and around the seagrass bed that are responsible for the suspension and deposition of sediment. To quantify these interactions, velocity, pressure, and sediment measurements were obtained across a density gradient of an eelgrass Zostera marina bed within a shallow coastal bay (1 to 2 m depth). Eelgrass beds were found to reduce near-bottom mean velocities by 70 to 90%, while wave heights were reduced 45 to 70% compared to an adjacent unvegetated region. Wave orbital velocities within the eelgrass bed were reduced by 20% compared to flow above the bed, primarily acting as a low-pass filter by removing high-frequency wave motion. However, relatively little reduction in wave energy occurred at lower wave frequencies, suggesting that longer period waves were able to effectively penetrate the seagrass meadow. Average bottom shear stresses (τb) at the unvegetated region were τb = 0.17 ± 0.08 N m–2, significantly larger than the critical stress threshold necessary for sediment entrainment of 0.04 N m–2. Within the eelgrass bed, τb = 0.03 ± 0.02 N m–2 and stresses were below the critical stress threshold during 80% of the time period of measurement. Expansion of eelgrass within the coastal bay has thus altered the dynamics of the seafloor from an erosional environment to one that promotes deposition of suspended sediment, enhancing light penetration throughout the water column and creating a positive feedback for eelgrass growth. KEY WORDS: Zostera marina · Seagrass · Waves · Turbulence · Boundary layer · Sediment resuspension Full text in pdf format PreviousNextCite this article as: Hansen JCR, Reidenbach MA (2012) Wave and tidally driven flows in eelgrass beds and their effect on sediment suspension. Mar Ecol Prog Ser 448:271-287. https://doi.org/10.3354/meps09225 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 448. Online publication date: February 23, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Nitrogen fixation in restored eelgrass meadows

Biological nitrogen (N2) fixation is the primary input of new nitrogen (N) to marine systems, and is important in meeting the N demands of primary producers. In this study, we deter- mined whether restoration of the eelgrass Zostera marina L. in a shallow coastal bay facilitated increasing rates of N2 fixation as the meadows aged. Rates of N2 fixation were measured in a system that had been devoid of eelgrass following local extinction in the 1930s until restoration by seeding began in 2001. Restored meadows of different ages were compared to nearby bare sediment sites during summer peak metabolism over 2 yr. Nutrient addition by N2 fixation was enhanced as the meadows aged. Rates of N2 fixation in the older (7 to 8 yr old) meadows were 2.7 times more than the younger (2 to 3 yr old) meadows (average 390 and 146 µmol N m �2 d �1 , respectively), and 28 times more than bare sediments (average 14 µmol N m �2 d �1 ). Heterotrophic epiphyte bacteria fixed approximately 90% of the total N2 in Z. marina meadows of both age classes. Both sediment and epiphyte N2 fixation were strongly related to Z. marina density and sediment organic content, suggesting that shoot density increases the positive feedback of plant presence on N2 fixation through the release of organic carbon exudates into the rhizosphere and phyllosphere, and the build up of sediment organic matter also increases. The N provided through fixation represented a large fraction (20.5 to 30%) of the total N demand to support eelgrass aboveground growth during this period of peak summertime production.

Stability and resilience of seagrass meadows to seasonal and interannual dynamics and environmental stress

Shallow coastal bays provide habitat for diverse fish and invertebrate populations and are an important source of sediment for surrounding marshes. The sediment dynamics of these bays are strongly affected by seagrass meadows, which limit sediment resuspension, thereby providing a more favorable light environment for their own survival and growth. Due to this positive feedback between seagrass and light conditions, it has been suggested that bare sediment and seagrass meadows are potential alternate stable states of the benthos in shallow coastal bays. To investigate the stability and resilience of seagrass meadows subjected to variation in environmental conditions (e.g., light, temperature), a coupled model of vegetation–sediment–water flow interactions and vegetation growth was developed. The model was used to examine the effect of dynamically varying seasonal and interannual seagrass density on sediment resuspension, water column turbidity, and the subsequent light environment on hourly time steps and then run over decadal time scales. A daily growth model was designed to capture both belowground biomass and the growth and senescence of aboveground biomass structural components (e.g., leaves and stems). This allowed us to investigate how the annual and seasonal variability in shoot and leaf density within a meadow affects the strength of positive feedbacks between seagrass and their light environment. The model demonstrates both the emergence of bistable behavior from 1.6 to 1.8 m mean sea level due to the strength of the positive feedback, as well as the limited resilience of seagrass meadows within this bistable range.

Eutrophication in shallow coastal bays and lagoons: the role of plants in the coastal filter

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 348:1-18 (2007) - DOI: https://doi.org/10.3354/meps07132 Eutrophication in shallow coastal bays and lagoons: the role of plants in the coastal filter Karen J. McGlathery1,*, Kristina Sundbäck2, Iris C. Anderson3 1Department of Environmental Sciences, University of Virginia, 291 McCormick Road, PO Box 400123, Charlottesville, Virginia 22903, USA 2Department of Marine Ecology, Marine Botany, Göteborg University, PO Box 461, 40530 Göteborg, Sweden 3School of Marine Science, Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia 23602, USA *Email: kjm4k@virginia.edu ABSTRACT: Nutrient loading to coastal bay ecosystems is of a similar magnitude as that to deeper, river-fed estuaries, yet our understanding of the eutrophication process in these shallow systems lags far behind. In this synthesis, we focus on one type of biotic feedback that influences eutrophication patterns in coastal bays—the important role of primary producers in the ‘coastal filter’. We discuss the 2 aspects of plant-mediated nutrient cycling as eutrophication induces a shift in primary producer dominance: (1) the fate of nutrients bound in plant biomass, and (2) the effects of primary producers on biogeochemical processes that influence nutrient retention. We suggest the following generalizations as eutrophication proceeds in coastal bays: (1) Long-term retention of recalcitrant dissolved and particulate organic matter will decline as seagrasses are replaced by algae with less refractory material. (2) Benthic grazers buffer the early effects of nutrient enrichment, but consumption rates will decline as physico-chemical conditions stress consumer populations. (3) Mass transport of plant-bound nutrients will increase because attached perennial macrophytes will be replaced by unattached ephemeral algae that move with the water. (4) Denitrification will be an unimportant sink for N because primary producers typically outcompete bacteria for available N, and partitioning of nitrate reduction will shift to dissimilatory nitrate reduction to ammonium in later stages of eutrophication. In tropical/subtropical systems dominated by carbonate sediments, eutrophication will likely result in a positive feedback where increased sulfate reduction and sulfide accumulation in sediments will decrease P adsorption to Fe and enhance the release of P to the overlying water. KEY WORDS: Eutrophication · Coastal bay · Lagoon · Nitrogen · Phosphorus · Seagrass · Macroalgae · Phytoplankton Full text in pdf format NextCite this article as: McGlathery KJ, Sundbäck K, Anderson IC (2007) Eutrophication in shallow coastal bays and lagoons: the role of plants in the coastal filter. Mar Ecol Prog Ser 348:1-18. https://doi.org/10.3354/meps07132 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 348. Online publication date: October 25, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Seasonal variations in dissolved organic carbon concentrations and characteristics in a shallow coastal bay

Dissolved organic matter (DOM) composition and dynamics in temperate shallow coastal bays are not well described although these bays may be important as local sources of organic carbon to ocean waters and are often sites of economically-important fisheries and aquaculture. In this study surface water samples were collected on a monthly to bi-monthly basis over two years from a mid-Atlantic coastal bay (Chincoteague Bay, Virginia and Maryland, USA). Dissolved organic carbon (DOC) concentrations and light absorbance characteristics were measured on sterile-filtered water, and high-molecular weight (> 1 kDa) dissolved OM (DOM) was isolated to determine stable isotope composition and molecular-level characteristics. Our time series encompassed both a drought year (2002) and a year of above-average rainfall (2003). During the dry year, one of our sites developed a very intense bloom of the brown tide organism Aureococcus anophagefferens while during the wet year there were brown tide bloom events at both of our sampling sites. During early spring of the wet year, there were higher concentrations of > 1 kDa DOC; this fraction represented a larger proportion of overall DOC and appeared considerably more allochthonous. Based upon colored dissolved organic matter (CDOM) and high-molecular weight DOM analyses, the development of extensive phytoplankton blooms during our sampling period significantly altered the quality of the DOM. Throughout both years Chincoteague Bay had high DOC concentrations relative to values reported for the coastal ocean. This observation, in conjunction with the observed effects of phytoplankton blooms on DOM composition, indicates that Chincoteague Bay may be a significant local source of “recently-fixed” organic carbon to shelf waters. Estimating inputs of DOC from Chincoteague Bay to the Mid-Atlantic Bight suggests that shallow productive bays should be considered in studies of organic carbon on continental shelves.

Variation in vegetation communities in shallow bays of the northern Baltic Sea

Macrophyte vegetation and different environmental factors were studied in shallow coastal bays with an opening threshold in three separate regions of the northern Baltic Sea. These bays are, due to isostatic land uplift, slowly cut off from the open sea and turn finally into shallow lakes. Depending on to which extent the shallow bays are connected to the open sea they are classified as succession stages, e.g. juvenile flad, flad, glo–flad and glo. Flads and gloes form important ecological units of the Baltic Sea in presenting rich animal and plant life. Distribution of vegetation in 18 bays was analyzed in order to study relations between species composition and the underlying morphological development of the bays. For this purpose, quantitative data on vegetation cover were analyzed by multivariate analyses. Obtained ordination scores were correlated to environmental data on morphometry and water quality. The ordination supported by the clustering revealed a clear concurrent succession gradient of bays and species, and the parameters best explaining this pattern were exposure, average depth of bay basin, cross-section area of the bay opening and suspended material. Species composition in earlier flads corresponded mainly to deep turbid brackish lake environments, whereas later succession stages were similar to those found in freshwaters. Turbidity reducing and stabilizing effects of macrophytes reported generally in lakes were confirmed in these bays, as well as the bioindicator capacity of Chara tomentosa. Our results verify applicability of a vegetation classification system previously stated for SW Finland, to the entire northern Baltic Sea.

Can different vegetative states in shallow coastal bays of the Baltic Sea be linked to internal nutrient levels and external nutrient load?

Can different vegetative states in shallow coastal bays of the Baltic Sea be linked to internal nutrient levels and external nutrient load?