Ferry-based monitoring of surface water quality in North Carolina estuaries

Several interrelated factors affect, water quality in the Albemarle-Pamlico Estuarine System (APES) including land use change in the upland and coastal watersheds, legislatively mandated basin-wide nutrient management plans, intense storms, and global and local changes in sea level. Despite its importance as an essential fish habitat, the APES has not been monitored as intensively or extensively for habitat impacts associated with decreased water quality as other estuaries have been, such as with the North Carolina tributary estuaries or Chesapeake Bay. To support the sustainable use of these estuaries, we are developing an automated water quality monitoring system aboard ferries that traverse the APES. This program, FerryMon, provides a unique, long-term, and cost-effective monitoring system to evaluate status and trends in APES water quality. Intensive temporal and spatial data obtained from all ferry routes provide an environmental baseline and are used to assess the patterns and variability in surface water hydrography, dissolved constituents, and particulate matter. The data are useful to calibrate estimates of ocean color and sea surface temperature from aircraft and satellite sensors. We are creating a searchable geographic database that is intended for scientists, managers, and the general public. Using ferries as sampling platforms to monitor estuarine water quality is a tractable approach and FerryMon represents a model for use in other large bodies of water traversed by ferries.     

Sources of nutrient pollution to coastal waters in the United States: Implications for achieving coastal water quality goals

Some 60% of coastal rivers and bays in the U.S. have been moderately to severely degraded by nutrient pollution. Both nitrogen (N) and phosphorus (P) contribute to the problem, although for most coastal systems N additions cause more damage. Globally, human activity has increased the flux of N and P from land to the oceans by 2-fold and 3-fold, respectively. For N, much of this increase has occurred over the past 40 years, with the increase varying by region. Human activity has increased the flux of N in the Mississippi River basin by 4-fold, in the rivers of the northeastern U.S. by 8-fold, and in the rivers draining to the North Sea by more than 10-fold. The sources of nutrients to the coast vary. For some estuaries, sewage treatment plants are the largest single input; for most systems nonpoint sources of nutrients are now of relatively greater importance, both because of improved point source treatment and control (particularly for P) and because of increases in the total magnitude of nonpoint sources (particularly for N) over the past three decades. For P, agricultural activities dominate nonpoint source fluxes. Agriculture is also the major source of N in many systems, including the flux of N down the Mississippi River, which has contributed to the large hypoxic zone in the Gulf of Mexico. For both P and N, agriculture contributes to nonpoint source pollution both through losses at the field scale, as soils erode away and fertilizer is leached to surface and ground waters, and from losses from animal feedlot operations. In the U.S. N from animal wastes that leaks directly to surface waters or is volatilized to the atmosphere as ammonia may be the single largest source of N that moves from agricultural operations into coastal waters. In some regions, including the northeastern U.S., atmospheric deposition of oxidized N from fossil-fuel combustion is the major flux from nonpoint sources. This atmospheric component of the N flux into estuaries has often been underestimated, particularly with respect to deposition onto the terrestrial landscape with subsequent export downstream. Because the relative importance of these nutrient sources varies among regions and sites, so too must appropriate and effective mitigation strategies. The regional nature and variability of nutrient sources require that nutrient management efforts address large geographic areas.     

Clay minerals in the major Chinese coastal estuaries and their provenance implications

A sea-survey was carried out along the Chinese coast from the Bohai Sea to South China Sea, and 15 surficial samples were taken from major coastal estuaries, i.e., from north to south, the Yellow, abandoned Yellow, Yangtze, Qiantang, Ou, Min, Han, and Pearl River estuaries. On the basis of clay mineral analysis and published data collection, this paper discusses the characteristics of clay minerals of each coastal river and potentials of implications of sediment sources. The results show that the change of diagnostic clay minerals from smectite to kaolinite from the Yellow to the Pearl River estuaries is southward, as clearly shown by the ratios of smectite to chlorite (S/Ch) and kaolinite to illite (K/I). S/Ch decreases southward, while K/I moves reversely, implying change in climate setting from cool/dry to humid/hot with intensified weathering processes. Besides, these two indicators in the estuaries are also linked with the derivation of parent-rock of each river-basin and coastal hydrodynamics. The disproportional higher ratio of K/I in the Yellow and abandoned Yellow River estuaries is ascribed to their sediment sources with abundant loess component in the north-central China. The K/I decrease offshore from the Pearl River estuary is primarily due to hydrodynamic sorting. Therefore, the S/Ch and K/I of the present study comprehensively reflect the controls of climate, parent-rock, and sediment transport along the coast.     

海洋次表层叶绿素最大值的特征因子及其影响因素

在多数情况下,海水中叶绿素垂直分布是不均匀的。次表层叶绿素最大值是其中较为常见的一种形式,普遍存在于大洋及沿岸海域。次表层叶绿素最大值层(SCML)的深度、厚度与强度是表征海洋次表层叶绿素最大值(SCM)现象的主要特征因子,受海洋水文环境、营养盐分布以及浮游植物种类等因素共同影响,在不同季节不同海区的分布有较大差异。总体上,相对近海,大洋中SCML特征因子的季节变化较小,SCML深度较大,厚度较大,强度较小。寡营养盐海区SCML深度及强度的影响因素研究已有较明确结论,SCML深度主要受物理因素(光照条件及水体混合程度)影响,而强度则受物理、生物因素(光照条件、水体混合程度或浮游动物摄食等)共同影响。近海富营养盐海区,SCML特征因子的影响因素研究较为薄弱。长时间序列、高分辨率观测站在相应海区的建立,对推进海洋SCM,尤其是近海SCM的研究有重要意义。卫星观测、现场观测和数学模型相结合,定量研究SCML特征因子与各物理、生物、化学因子的普适性关系,是进一步研究SCML特征因子的重要方向之一。     

Coastal flooding in Scotland: towards national-level hazard assessment

This study investigated contributory factors to flood hazard around Scotland. There is a need to develop preliminary assessments of areas potentially vulnerable to flooding for compliance with the European Union Directive on the Assessment and Management of Flood Risks (2007/60/EC). Historical accounts of coastal flood events in Scotland, notably in a storm in January 2005, had shown that estimates of risk based on still water levels required further information to identify sites at which waves and surges could combine. Additionally, it was important to add the effect of future sea-level rise and other drivers from published sources. Analysis of multiple years’ tidal data at seven sites, including estuaries, compared recorded water levels at high-return periods to those derived from a spatially interpolated numerical model contained within a publicly available flood risk map. For gauges with the longest records, increases were seen over time that reflected rises in mean sea level. Exposure to wave energy was computed from prevailing wind strength and direction at 36 stations, related to wave fetch and incident wind direction. Although the highest wave exposure was at open coast locations exposed to the long Atlantic fetch, GIS analysis of coastal rasters identified other areas in or close to estuaries that also had high exposure. Projected sea-level change, when added to the surge and wave analyses, gives a spatially extensive structured variable flood risk assessment for future coastal flood hazard to complement the public flood risk map. Such tools can help fulfil the requirements of the EC Directive and may be a useful approach in other regions with high spatial variability in coastal flood risk related to exposure to waves and wind.     

Variability of the mixing zones and estuarine turbidity maxima in the Elbe and Weser estuaries

The neighboring coastal plain estuaries of the Elbe and Weser Rivers in Northern Germany exhibit pronounced estuarine turbidity maxima (ETM). Common features and differences between the longitudinal distributions of salinity and suspended particulate matter (SPM) in both estuaries are compared as well as the mechanisms effecting them. Monthly transects of the near surface SPM indicate that the long-term variability of salinity and the ETM is mainly influenced by the freshwater runoff. The variability is reduced to certain characteristic patterns by application of Empirical Orthogonal Functions analysis. The coefficients of these patterns are then correlated to runoff and the resulting functional regressions are used for the construction of a statistical model for the distribution of salinity and SPM along the estuaries; for SPM this has not been successful.     

Classification of clastic coastal depositional environments

This paper proposes a new classification for clastic coastal environments which includes the full range of major depositional settings including deltas, strand plains, tidal flats, estuaries and lagoons. This classification includes both morphologic and evolutionary components and is based on dominant coastal processes. It has the potential to predict responses in geomorphology, facies and stratigraphy. The significance of this classification is its evolutionary capability, and its inclusion of all major clastic coastal depositional environments, making it more comprehensive than previous classifications.

We employ a ternary process classification with two axes. The first (horizontal axis) is defined as the relative power of wave versus tidal processes. The second (vertical) axis represents relative fluvial power (increasing upward). A ternary diagram defined by these axes can be used to illustrate the genetic process-response relationships between major coastal environments. The evolutionary classification combines the concept of two sediment sources (river and marine) with a relative sea-level parameter to classify embayed as well as linear and elongate/lobate shorelines. This approach identifies the evolutionary relationships between coastal sedimentary environments.

The new ternary approach to process classification can be applied to estuaries and lagoons to define wave and tide end-member facies models, each consisting of a tripartite facies zonation. The evolutionary classification is compatible with sequence stratigraphy because sediment supply and relative sea level are included, and serves as a starting point for more refined coastal stratigraphic analyses.     

Challenges and strategies for better use of scientific information in the management of coastal estuaries

Numerous studies have concluded that better use of scientific information could improve the quality of coastal and estuarine environmental management. Approaches for effecting such a change include ecosystem-based, integrated, and adaptive management, but such basic re-orientation of estuarine and coastal management has proved difficult to achieve. Even environmental indicators, seemingly straightforward ways of injecting scientific information into decision making, have achieved broad on-the-ground use in relatively few instances—principally the largest estuary management programs. A conceptual framework useful for examining environmental management systems affecting the five PNCERS (Pacific Northwest coastal Ecosystems Regional Study) estuaries conceives of environmental managers, researchers, and interested and affected parties in the public as interacting through the multi-layered institutional arrangements that currently promote the utilization, management, or protection of coastal and estuarine resources. Considerable variation exists in the approach and effectiveness of the region's environmental management organizations. Interaction between science and management in the region appears to be limited to an extent by high transaction costs; a cultural divide between environmental scientists and environmental managers is perceived by members of both groups who work with the PNCERS estuaries as inhibiting communications between them. Mechanisms that both groups identify as useful for improving the flow of information between science and management are little used, perhaps as a result. The two groups have very different patterns of information dissemination and acquisition, and though both chose agency archives and databases as their top methods for disseminating information, neither group relies much on these vehicles for information they seek. Both residents' and practitioners' perceptions of threats to the PNCERS estuaries show patterns of estuary-to-estuary variation. One theme that emerges is that problems associated with poor land management in adjacent uplands are common to most of these estuaries, potentially providing a sense of commonality through which a more regional approach to estuary management could emerge. A common set of estuarine environmental indicators implemented for all estuaries could help instigate such a regional approach, but resource constraints, especially at the local level, will have to be overcome for that to occur. There is currently substantial lack of common vision among coastal practitioners as to the purpose and desirability of indicators, and relatively little experience or knowledge of their use, particularly at the local level. Use of estuarine science in the management of these estuaries appears to be greatest during periods in which the largest programmatic shifts in environmental management approaches occur, an observation consistent with other studies that have concluded that the use of environmental science in environmental management tends to be episodic.     

气溶胶质谱技术在海洋气溶胶亚微米级颗粒物特征的研究进展

海洋上空颗粒物(即海洋气溶胶)体系组成和来源非常复杂,它对于大气颗粒物总数贡献非常大,是大气科学及全球变化领域研究的重要组成部分。与传统离线滤膜采样技术相比,气溶胶质谱技术具有灵敏度高、检测效率高、时空分辨率高等特点,已广泛应用于大气细颗粒物的特征和来源判别研究中。综述比较了目前应用最广泛的气溶胶质谱仪(AMS)和气溶胶飞行时间质谱仪(ATOFMS)在岛屿、沿海城市、近海、开阔大洋及南北极地等区域细颗粒物特征的研究进展。指出2种一起联合使用,可以较为全面地观测海洋气溶胶的粒径、化学组分及混合态的特征,为中国近海的雾霾监测网建设和治理空气污染提供一定的科学依据。     

Coastal-Zone Biogeochemical Dynamics under Global Warming

The coastal zone, consisting of the continental shelves to a depth of 200 meters, including bays, lagoons, estuaries, and near-shore banks, is an environment that is strongly affected by its biogeochemical and physical interactions with reservoirs in the adjacent domains of land, atmosphere, open ocean, and marine sediments. Because the coastal zone is smaller in volume and areal coverage relative to the open ocean, it traditionally has been studied as an integral part of the global oceans. In this paper, we show by numerical modeling that it is important to consider the coastal zone as an entity separate from the open ocean in any assessment of future Earth-system response under human perturbation. Model analyses for the early part of the 21st century suggest that the coastal zone plays a significant modifying role in the biogeochemical dynamics of the carbon cycle and the nutrient cycles coupled to it. This role is manifested in changes in primary production, storage, and/or export of organic matter, its remineralization, and calcium carbonate precipitation- all of which determine the state of the coastal zone with respect to exchange of CO₂ with the atmosphere. Under a scenario of future reduced or complete cessation of the thermohaline circulation (THC) of the global oceans, coastal waters become an important sink for atmospheric CO₂, as opposed to the conditions in the past and present, when coastal waters are believed to be a source of CO₂, to the atmosphere. Profound changes in coastal-zone primary productivity underscore the important role of phosphorus as a limiting nutrient. In addition, our calculations indicate that the saturation state of coastal waters with respect to carbonate minerals will decline by ～15% by the year 2030. Any future slowdown in the THC of the oceans will increase slightly the rate of decline in saturation state.     

Estuaries of the northeastern United States: Habitat and land use signatures

Geographic signatures are physical, chemical, biotic, and human-induced characteristics or processes that help define similar or unique features of estuaries along latitudinal or geographic gradients. Geomorphologically, estuaries of the northeastern U.S., from the Hudson River estuary and northward along the Gulf of Maine shoreline, are highly diverse because of a complex bedrock geology and glacial history. Back-barrier estuaries and lagoons occur within the northeast region, but the domiant type is the drowned-river valley, often with rocky shores. Tidal range and mean depth of northeast estuaries are generally greater when compared to estuaries of the more southern U.S. Atlantic coast and Gulf of Mexico. Because of small estuarine drainage basins, low riverine flows, a bedrock substrate, and dense forest cover, sediment loads in northeast estuaries are generally quite low and water clarity is high. Tidal marshes, seagrass meadows, intertidal mudflats, and rocky shores represent major habitat types that fringe northeast estuaries, supporting commercially-important fauna, forage nekton and benthos, and coastal bird communities, while also serving as links between deeper estuarine waters and habitats through detritus-based pathways. Regarding land use and water quality trends, portions of the northeast have a history of over a century of intense urbanization as reflected in increased total nitrogen and total phosphorus loadings to estuaries, with wastewater treatment facilities and atmospheric deposition being major sources. Agricultural inputs are relatively minor throughout the northeast, with relative importance increasing for coastal plain estuaries. Identifying geographic signatures provides an objective means for comparing the structure, function, and processes of estuaries along latitudinal gradients.     

Climatic and Tidal Forcing of Hydrography and Chlorophyll Concentrations in the Columbia River Estuary

Hydrographic patterns and chlorophyll concentrations in the Columbia River estuary were compared for spring and summer periods during 2004 through 2006. Riverine and oceanic sources of chlorophyll were evaluated at stations along a 27-km along-estuary transect in relation to time series of wind stress, river flow, and tidal stage. Patterns of chlorophyll concentration varied between seasons and years. In spring, the chlorophyll distribution was dominated by high concentrations from freshwater sources. Periods of increased stream flow limited riverine chlorophyll production. In summer, conversely, upwelling winds induced input of high-salinity water from the ocean to the estuary, and this water was often associated with relatively high chlorophyll concentrations. The frequency, duration, and intensity of upwelling events varied both seasonally and interannually, and this variation affected the timing and magnitude of coastally derived material imported to the estuary. The main source of chlorophyll thus varied from riverine in spring to coastal in summer. In both spring and summer seasons and among years, modulation of the spring/neap tidal cycle determined stratification, patterns of mixing, and the fate of (especially freshwater) phytoplankton. Spring tides had higher mixing and neap tides greater stratification, which affected the vertical distribution of chlorophyll. The Columbia River differs from the more tidally dominated coastal estuaries in the Pacific Northwest by its large riverine phytoplankton production and transfer of this biogenic material to the estuary and coastal ocean. However, all Pacific Northwest coastal estuaries investigated to date have exhibited advection of coastally derived chlorophyll during the upwelling season. This constitutes a fundamental difference between Pacific Northwest estuaries and systems not bounded by a coastal upwelling zone.     

莱州湾南岸滨海湿地生物多样性及生态地质环境变化

莱州湾南岸滨海湿地作为环渤海滨海湿地的一部分,具有海洋与河口交互性、海陆过渡性和生态脆弱性等特点,湿地面积广阔、资源丰富,是东北亚环西太平洋鸟类迁徙的重要“中转站”及越冬、栖息和繁殖地。湿地总面积为1150．079km^2,湿地维管束植物区系包括维管束植物53科144属217种。近年来,在对滨海湿地的开发中,虾池、盐田等人工湿地面积不断扩大,造成自然湿地面积减小、植被退化、地貌和水文条件改变、生物多样性下降,改变了原始的滨海湿地自然景观,破坏了珍稀鸟类的生存环境。     

Influence of Hydrological Regime in Determining the Response of Macroalgal Blooms to Nutrient Loading in Two Irish Estuaries

Eutrophication and the development of persistent opportunistic macroalgal blooms are recognised as one of the main detrimental effects of increased anthropogenic pressures on estuarine and coastal systems. This study aimed to highlight the interplay between pressures and controlling physical factors on ecosystem functioning. The hypothesis that hydrological regime can control the growth of opportunistic macroalgae was tested with the study of two Irish estuaries, the Argideen and the Blackwater, with similar nutrient loading sources but divergent hydrological regimes. Seasonal monitoring data was initially examination, while the application of a pre-existing box model allowed a further analysis of the influence of residence time and nutrient load modifications on macroalgal growth. Seasonal oscillations in monitored river flow rates altered nutrient transfer from the catchments to the estuaries in both cases, as is shown through differences between winter and summer nutrient concentrations. In the Argideen, however, the relative contribution of phosphorus (P) from adjacent marine waters was high due to the shorter residence times and greater influx of marine water into the estuary. Modelling studies showed that in the Argideen Estuary, P load reduction would have potentially minimal impact on macroalgal growth due to the shorter residence time which increased the influx of P from marine sources. Nitrogen (N) load reduction of 60 % had a significant, albeit limited, impact on macroalgae and was insufficient in achieving the environmental objectives for this waterbody. For the more river-dominated Blackwater Estuary, modelled reductions in P resulted in a considerable decrease in biomass. Any further P decreases would accentuate the existing disparity in estuarine N:P ratios with possible repercussions for N transport to the coastal system. Hence, the hydrological complexity of estuarine systems demonstrated dictates that a portfolio of separate, but complimentary, management approaches may be required to address eutrophication in these estuaries.     

Flooding trends and their impacts on coastal communities of Western Cape Province,South Africa

Climate change-induced extreme weather events have been at their worst increase in the past decade (2010–2020) across Africa and globally. This has proved disruptive to global socio-economic activities. One of the challenges that has been faced in this regard is the increased coastal flooding of cities. This study examined the trends and impacts of coastal flooding in the Western Cape province of South Africa. Making use of archival climate data and primary data from key informants and field observations, it emerged that there is a statistically significant increase in the frequency of flooding and consequent human and economic losses from such in the coastal cities of the province. Flooding in urban areas of the Western Cape is a factor of human and natural factors ranging from extreme rainfall, usually caused by persistent cut off-lows, midlatitude cyclones, cold fronts and intense storms. Such floods become compounded by poor drainage caused by vegetative overgrowth on waterways and land pollution that can be traced to poor drainage maintenance. Clogging of waterways and drainage systems enhances the risk of flooding. Increased urbanisation, overpopulation in some areas and non-adherence to environmental laws results in both the affluent and poor settling on vulnerable ecosystems. These include coastal areas, estuaries, and waterways, and this worsens the risk of flooding. The study recommends a comprehensive approach to deal with factors that increase the risk of flooding as informed by the provisions of both the Sustainable Development Goals framework and the Sendai Framework for Disaster Risk Reduction 2015–2030 in a bid to de-risking human settlement in South Africa.

     

A review of land–sea coupling by groundwater discharge of nitrogen to New England estuaries: Mechanisms and effects

Hydrologists have long been concerned with the interface of groundwater flow into estuaries, but not until the end of the last century did other disciplines realize the major role played by groundwater transport of nutrients to estuaries. Mass balance and stable isotopic data suggest that land-derived NO₃, NH₄, and dissolved organic N do enter estuaries in amounts likely to affect the function of the receiving ecosystem. Because of increasing human occupancy of the coastal zone, the nutrient loads borne by groundwater have increased in recent decades, in spite of substantial interception of nutrients within the land and aquifer components of watersheds. Groundwater-borne nutrient loads have increased the N content of receiving estuaries, increased phytoplankton and macroalgal production and biomass, decreased the area of seagrasses, and created a cascade of associated ecological changes. This linkage between land use and eutrophication of estuaries occurs in spite of mechanisms, including uptake of land-derived N by riparian vegetation and fringing wetlands, “unloading” by rapid water removal, and direct N inputs to estuaries, that tend to uncouple the effects of land use on receiving estuaries. It can be expected that as human activity on coastal watersheds continues to increase, the role of groundwater-borne nutrients to the receiving estuary will also increase.     

Nutrient biogeochemistry in an upwelling-influenced estuary of the Pacific northwest (Tillamook Bay,Oregon, USA)

Tillamook Bay, Oregon, is a drowned river estuary that receives freshwater input from 5 rivers and exchanges ocean water through a single channel. Similar to other western United States estuaries, the bay exhibits a strong seasonal change in river discharge in which there is a pronounced winter maximum and summer minimum in precipitation and runoff. The behavior of major inorganic nutrients (phosphorus, nitrogen, and silica) within the watershed is examined over seasonal cycles and under a range of river discharge conditions for October 1997–December 1999. Monthly and seasonal sampling stations include transects extending from the mouth of each river to the mouth of the estuary as well as 6–10 sites upstream along each of the 5 major rivers. Few studies have examined nutrient cycling in Pacific Northwest estuaries. This study evaluates the distributions of inorganic nutrients to understand the net processes occurring within this estuary. Based upon this approach, we hypothesize that nutrient behavior in the Tillamook Bay estuary can be explained by two dominant factors: freshwater flushing time and biological uptake and regeneration. Superimposed on these two processes is seasonal variability in nutrient concentrations of coastal waters via upwelling. Freshwater flushing time determines the amount of time for the uptake of nutrients by phytoplankton, for exchange with suspended particles, and for interaction with the sediments. Seasonal coastal upwelling controls the timing and extent of oceanic delivery of nutrients to the estuary. We suggest that benthic regeneration of nutrients is also an important process within the estuary occurring seasonally according to the flushing characteristics of the estuary. Silicic acid, nitrate, and NH₄ ⁺ supply to the bay appears to be dominated by riverine input. PO₄ ⁻³ supply is dominated by river input during periods of high river flow (winter months) with oceanic input via upwelling and tidal exchange important during other times (spring, summer, and fall months). Departures from conservative mixing indicate that internal estuarine sources of dissolved inorganic phosphorus and nitrogen are also significant over an annual cycle.     

Wind-driven sediment suspension controls light availability in a shallow coastal lagoon

Light availability is critically important for primary productivity in coastal systems, yet current research approaches may not be adequate in shallow coastal lagoons. Light attenuation in these systems is typically dominated by suspended sediment, while light attenuation in deeper estuaries is often dominated by phytoplankton. This difference in controls on light attenuation suggests that physical processes may exert a greater influence on light availability in coastal lagoons than in deeper estuaries. Light availability in Hog Island Bay, a shallow coastal lagoon on the eastern shore of Virginia, was determined for a summer and late fall time period with different wind conditions. We combined field measurements and a process-based modeling approach that predicts sediment suspension and light availability from waves and currents to examine both the variability and drivers of light attenuation. Total suspended solids was the only significant predictor of light attenuation in Hog Island Bay. Waves and currents in Hog Island Bay responded strongly to wind forcing, with bottom stresses from wind driven waves dominant for 60% of the modeled area for the late fall period and 24% of the modeled area for the summer period. Higher wind speeds in late fall than in summer caused greater sediment suspension (41 and 3 mg l⁻¹ average, respectively) and lower average (spatial and temporal) downwelling light availability (32% and 55%, respectively). Because of the episodic nature of wind events and the spatially variable nature of sediment suspension, conventional methods of examining light availability, such as fair-weather monitoring or single in situ recorders, do not adequately represent light conditions for benthic plants.     

Patterns of estuarine use by juvenile English sole (Parophrys vetulus) and Dungeness crab (Cancer magister)

Extensive trawl surveys were conducted in two large estuaries (Grays Harbor and Willapa Bay) on the Washington coast during 1983–1987, and in adjacent areas of the open coast. These surveys have shown that both English sole and Dungeness crab rely heavily on these estuaries as nursery areas, although the pattern of utilization differs substantially. Juvenile migration patterns can show substantial interannual variability and can only be delineated by concurrent surveys in both coastal and estuarine areas, conducted over a period of several years. English sole eggs and Dungeness crab larvae are released in coastal waters. Larvae of both species transform to the benthic stage in both coastal and estuarine areas, but most English sole eventually migrate into the estuaries during the first year of life, even if initial settlement is along the open coast. By the time English sole have attained a length of 55 mm (TL), most of them are found in estuaries. English sole begin emigrating from the estuaries at about 75 mm, and few remain there during the second year of life. In contrast, Dungeness crab appear to remain in the area of initial settlement throughout the first year of life. Growth is substantially faster in estuaries where 0+ crab reach a mean size of about 40 mm carapace width (CW) by September, with those off the coast are only about 14 mm CW. Juveniles remain in the area of settlement over their first winter but, in contrast to English sole, most coastal 1+ crab immigrate to estuaries to join siblings that settled there the previous year. By September of the second year, crab at about 100 mm CW emigrate to the open coast where they reach maturity. Advantages to juvenile stages that reside in estuaries are discussed in terms of accelerated growth at higher temperatures and potentially greater food supplies than found nearshore along the coast.     

Nitrogen loads to estuaries: Using loading models to assess the effectiveness of management options to restore estuarine water quality

Nitrogen (N) loading to estuaries has become a major concern for coastal planners. As urban development on coastal watershed continues, estuaries and bays are becoming more eutrophic, and cascading effects are being felt at every trophic level. Managers and stakeholders need to have a suite of effective management tools that can be applied to coastal watersheds to minimize the effects of eutrophication. We applied an N loading model and an estuarine loading model to examine the effectiveness of a suite of potential management options that could be implemented in Waquoit Bay, Cape Cod, Massachusetts. This estuarine system is a case study in which we can explore the relative potential effectiveness of decreasing inputs from wastewater and fertilizer-derived N, diverting nitrogenous runoff from impervious surfaces, altering zoning ordinances, preserving forested tracts of land as well as freshwater and saltwater wetlands, harvesting macroalgae, dredging estuary channels, and exterminating waterfowl. From a combination of simulation results, assessment of the magnitude of loads from different sources, and through different land covers, and the additional consideration of feasibility we identified management options with high, intermediate, and low potential effectiveness. Improvement of septic system performance, use of zoning regulations, preservation of forested tracts and freshwater bodies, and conservation of salt marshes emerged as the most promising avenues to manage N loads in our system. Installation of wastewater treatment plants, controlling fertilizer use, and harvesting macroalgae would potentially have intermediate success. Diversion of runoff from impervious surfaces, dredging, and extermination of waterfowl show little promise at reducing N loads. These conclusions potentially set priorities for decision-makers charged with the management of Waquoit Bay. The same procedures applied to another watershed-estuary system with different land covers and different estuarine features may differ. Evaluation studies like this need to be done for any particular site, since the watershed-estuary coupling and the loads delivered to the receiving estuary could differ. The Waquoit Bay case study provides an example of a protocol that leads to identification of the most promising management options.