Challenges in Estuarine and Coastal Science

Estuarine and coastal waters are acknowledged centres for anthropogenic impacts. Superimposed on the complex natural interactions between land, rivers and sea are the myriad consequences of human activity – a spectrum ranging from locally polluting effluents to some of the severest consequences of global climate change. For practitioners, academics and students in the field of coastal science and policy, this book examines and exemplifies current and future challenges: from upper estuaries to open coasts and adjacent seas; from tropical to temperate latitudes; from Europe to Australia. This authoritative volume marks the 50th anniversary of the Estuarine and Coastal Sciences Association, and contains a prologue by founding member Professor Richard Barnes and a short history of the Association. Individual chapters then address coastal erosion and deposition; open shores to estuaries and deltas; marine plastics; coastal squeeze and habitat loss; tidal freshwaters – saline incursion and estuarine squeeze; restoration management using remote data collection; carbon storage; species distribution and non-natives; shorebirds; Modelling environmental change; physical processes such as sediments and modelling; sea level rise and estuarine tidal dynamics; estuaries as fish nurseries; policy versus reality in coastal conservation; developments in Estuarine, coastal and marine management.

Tidal mixing of estuarine and coastal waters in the Western English Channel controls spatial and temporal variability in seawater CO₂

Surface ocean CO2 measurements are used to compute the oceanic air–sea CO2 flux. The CO2 flux component from rivers and estuaries is uncertain. Estuarine and coastal water carbon dioxide (CO2) observations are relatively few compared to observations in the open ocean. The contribution of these regions to the global air–sea CO2 flux remains uncertain due to systematic under-sampling. Existing high-quality CO2 instrumentation predominantly utilise showerhead and percolating style equilibrators optimised for open ocean observations. The intervals between measurements made with such instrumentation make it difficult to resolve the fine-scale spatial variability of surface water CO2 at timescales relevant to the high frequency variability in estuarine and coastal environments. Here we present a novel dataset with unprecedented frequency and spatial resolution transects made at the Western Channel Observatory in the south west of the UK from June to September 2016, using a fast response seawater CO2 system. Novel observations were made along the estuarine–coastal continuum at different stages of the tide and reveal distinct spatial patterns in the surface water CO2 fugacity (fCO2) at different stages of the tidal cycle. Changes in salinity and fCO2 were closely correlated at all stages of the tidal cycle and suggest that the mixing of oceanic and riverine end members determines the variations in fCO2. The observations demonstrate the complex dynamics determining spatial and temporal patterns of salinity and fCO2 in the region. Spatial variations in observed surface salinity were used to validate the output of a regional high resolution hydrodynamic model. The model enables a novel estimate of the air–sea CO2 flux in the estuarine–coastal zone. Air–sea CO2 flux variability in the estuarine–coastal boundary region is dominated by the state of the tide because of strong CO2 outgassing from the river plume. The observations and model output demonstrate that undersampling the complex tidal and mixing processes characteristic of estuarine and coastal environment bias quantification of air-sea CO2 fluxes in coastal waters. The results provide a mechanism to support critical national and regional policy implementation by reducing uncertainty in carbon budgets.

A new species of Bestiolina (Copepoda, Calanoida, Paracalanidae) and complementary description of B. similis (Sewell, 1914) from the Nansei Islands, Japan

Two species of the calanoid copepod genus Bestiolina occurred in estuarine/coastal waters of the Nansei Islands, southernmost Japan. One of them is described herein as Bestiolina okinawae sp. nov., which is distinguished from known congeners by a combination of the following characteristics: 1) fifth pedigerous somite bearing groups of tiny spinules on the posterior end, 2) female mandible bearing a rod-shaped first gnathal tooth, 3) male left leg 5 with short apical spine on long terminal segment, and 4) legs 2–3 with endopodal segment 2 lacking spinules. The new species was the dominant zooplankter in oligohaline waters. The other species is morphologically identifiable to Bestiolina similis (Sewell, 1914). Genetic analysis using COI revealed that the two species differed by 9.9–10.0%, in contrast to small intra-specific genetic variation (0.0–1.5%). The two species were spatially segregated in low-salinity (2–30) estuaries and high-salinity (25–36) coastal waters, respectively, but co-occurred in some samples. Their body length decreased from the winter (around 20°C) to the summer (around 30°C) by 9.5–18.1%, depending on the species and sex. In both species, adult males, which lack mandibular gnathobase, were larger than the adult females.

Impacts of Deepwater Horizon on Fish and Fisheries: What Have we Learned about Resilience and Vulnerability in a Coupled Human-Natural System?

The Deepwater Horizon (DWH) oil spill occurred in a region of the Gulf of Mexico (GoM) supporting abundant, diverse and valuable communities of fishes and fishers. The economy of the northern GoM is inextricably tied to the natural resource bases of the region (tourism, fishing, oil and gas, etc.) and thus the coupling between the human and ecological systems is tight and subject both feed-back and, to some extent, feed-forward controls. Management actions taken during the 87-day DWH spill incident included the closure of over 280,000 km2 of productive fishing area (about 1/3 of USA federal waters in the GoM), resulting in significant declines in catches and revenues for some critical species for several months after the spill. As well, a variety of oil spill countermeasures including the use of chemical dispersants (at the well head and the sea surface), releases of freshwater into marshes to staunch the progression of oil ashore, creation of sand berms, burning of oil at sea and mechanical pickup were employed. Because of the closures, fishers were compensated for lost fishing opportunities in a number of ways, including employment in oil spill response efforts (the VoO or Vessel of Opportunity program), accepting compensation payments from the Responsible Parties, and moving fishing areas and shifting to open areas of the GoM. Some fisheries were heavily impacted during 2010 (e.g., menhaden and inshore invertebrate fisheries), while for others, area shifting resulted in little change in GoM-wide fishery catches (e.g., red snapper, penaeid shrimps). In the 10 years since the DWH disaster, many fisheries have recovered, exhibiting patterns of inter-annual variability consistent with those seen prior to the spill, but other species have shown little to no recovery. One of the critical issues in understanding oil spill effects is that of causal inference given multiple simultaneous drivers and feedbacks, thus the appeal of viewing fish-fishery interactions as a coupled human and natural system. Results of long-term monitoring studies document a variety of responses of various taxa occupying diverse habitats from estuarine/coastal to open ocean. These impacts resulted both from oil contamination and from various response countermeasures. Differential recovery trajectories are mediated by life history aspects contributing to resilience and to some extent the degree of ongoing contamination from pools of residual oil and other chronic sources. Relatively resilient species were those exhibiting low to moderate modularity (near ubiquitous species or populations) and those with relatively short life cycles. Fishing community resilience to the spill was related to a variety of employment alternatives during closures and facilitated by the capacity of fishers to adapt to non-traditional opportunities in fishing and by financial assistance programs. Overall, the level of business failures during and just after DWH was lower than historical averages for important reef fish fisheries of the Gulf.

Variability of river plume in the Gulf of Tonkin

<p>The quality of estuarine, coastal and marine environment in the Gulf of Tonkin, in the South China Sea, is an essential issue to the ecosystems’ health and to the living conditions and economy of the Viet Nam population. The stakes are particularly high since the demographic density in the Red River delta is one of the highest in the world. Understanding the physical processes that drive the ocean circulation and its response to anthropic pressure there is therefore of primarily importance for enlightened resource management, as well as for designing adequate monitoring and forecasting systems.</p><p>As a first step toward a better understanding of the physical coastal and marine environment, we present here a study on the Red river plume variability in the Gulf of Tonkin over the period 2011-2016. The study is based on a numerical simulation, under realistic conditions, using the SYMPHONIE coastal model developed at LEGOS (Marsaleix et al., 2008). Compared with various data sources, the model results show good performances. The river plume is then identified and examined at different time scales. In general, the surface coverage of the river plume is strongly correlated with the runoff but with a 1-month lag. However, in some years, a higher peak in runoff does not create a higher peak of the plume area, suggesting that other forcings need to be taken into account to explain the variability of the river plume.</p><p>Using K-mean clustering, the main patterns of the plume are identified. The result shows that the plume has a large variability at both seasonal and interannual scales. Each pattern shows the plume under different forcing conditions.  Most of the time, the plume is narrow and sticks along the coast due to the downcoast current and northeasterly wind. In the summer, due to monsoon, the wind direction changes to southwesterly and helps the plume to spread offshore. The plume reaches its highest coverage in September after the peak of runoff; then its coverage decreases again when the monsoon reverses.</p><p>We also analyze events of offshore export of freshwater at daily time scales and show that they can be associated with recurrent coastal eddies during the summer monsoon. We investigate the respective role of wind and runoff in the eddies formation. Comparison with a run without river allows to identify the main impacts of the plume on the ocean states, for example in the current and sea surface elevation.</p>

Plankton Community Metabolism in Western Australia: Estuarine, Coastal and Oceanic Surface Waters

Net community production (NCP) is a community level process informing on the balance between production and consumption, determining the role of plankton communities in carbon and nutrient balances fueling the marine food web. An assessment of net and gross community production (NCP, GPP) and community respiration (CR) in 86 surface plankton communities sampled between 15° and 36° South along coastal Western Australia (WA) revealed a prevalence of net autotrophic metabolism (GPP/CR > 1), comprising 81% of the communities sampled. NCP, GPP, and CR decreased with decreasing nutrient and chlorophyll-a concentrations, from estuarine, to coastal and oceanic waters. CR, standardized per unit chlorophyll-a, increased with temperature, with higher activation energies (Ea) than GPP per unit chlorophyll-a (Ea 1.07 ± 0.18 eV and 0.65 ± 0.15 eV, respectively) either across ecosystem types and for coastal and estuary communities alone, indicating plankton CR to increase much faster with warming than GPP. These results characterize surface plankton communities across Western Australia as CO2 sinks, the stronger thermal-dependence of respiration that gross primary production rates suggests that their role may weaken with future warming.