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Coastal & Estuarine Science News (CESN)

Coastal & Estuarine Science News (CESN) is an electronic publication providing brief summaries of select articles from the journal Estuaries & Coasts that emphasize management applications of scientific findings. It is a free electronic newsletter delivered to subscribers on a bimonthly basis.

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2016 January


When Seagrass is Scarce, Can Fringing Marsh Fill the Gap?
Australian Fish Ride the Tide
Wetlands Loss in the Pacific Northwest and Salmon Density-Dependence
Building the Data Infrastructure of the Future

When Seagrass is Scarce, Can Fringing Marsh Fill the Gap?

Marshes may provide habitat for fish and inverts in the face of seagrass loss in the Gulf of Mexico

Seagrass meadows are a critical ecosystem component of many coastal areas, providing habitat for a wide range of species, but they are also threatened and in decline worldwide. A ray of hope for seagrass-associated species was uncovered by a recent study of lagoon systems in the Gulf of Mexico, where many lagoons contain both seagrass meadows and fringing marshes. Could the marshes “pick up the slack” for imperiled seagrass beds? 

The study examined abundances of a range of fish and macroinvertebrate species over two years at lagoon sites with varying degrees of seagrass meadow cover; all sites also had fringing marsh. As the investigators hypothesized, there was no significant relationship between seagrass cover and fish and macroinvertebrate abundance for ten seagrass-associated taxa or for overall epifaunal abundance. Part of the explanation, the authors state, is that the nearby marshes might be providing habitat redundancy, in particular serving the same predator refuge function. The authors believe that the shallowness of the lagoons studied (all less than 1 m deep) may also provide refuge from predators in the absence of seagrass. A third compensatory factor could be the presence of marsh detrital debris, which appears to support epifaunal communities when seagrass is lacking, thereby indirectly supporting higher trophic levels like seagrass-associated fish and macroinvertebrates. These results imply that shallow lagoons in the Gulf are good habitat for fish and invertebrates regardless of seagrass cover; all habitat types should be considered holistically when managing communities. 

Source: McDonald, R. B., R. M. Moody, K. L. Heck, and J. Cebrian. 2015. Fish, macroinvertebrate and epifaunal communities in shallow coastal lagoons with varying seagrass cover of the northern Gulf of Mexico. Estuaries and Coasts (November 2015). DOI:  10.1007/s12237-015-0031-7

Australian Fish Ride the Tide

Acoustic camera data reveal that fish movement through a narrow estuary mouth is related to tidal flow

Fish can provide a critical ecological link between estuaries and the nearby coastal ocean, as many species move in and out of estuaries depending on life stage, time of year, tidal cycle, prey movement, and other factors. But not much is known about the fine-scale timing, direction, and behavior of fish movement. A study using a DIDSON acoustic camera in a small Australian estuary was able to capture video of the entire estuary entrance over a 4-month period to examine exactly how many fish came and went, whether they were schooling, and the timing of their excursions. 

Greater numbers of fish entered the estuary on flood tides, indicating that fish “ride the tide” most of the time but some do swim against the tidal current, particularly entering the estuary on ebb tides. Peak traffic times for fish occurred during the middle of the tidal cycle, whether on flood or ebb tides. Incoming fish were far more likely to swim in schools than those exiting. The authors speculate that this behavior may assist in predator avoidance during the dicey transit between the ocean and the estuary, or it may be a kind of piscine “crowd-sourcing”: a school of fish traveling together in the ocean may make better decisions about which estuaries to enter than a single fish. This type of fine-scale information about fish movements and linkages among ecosystems can benefit managers engaged in marine spatial planning, fisheries management, habitat restoration, or other types of initiatives.

Source: Becker, A., M. Holland, J. A. Smith, and I. M. Suthers. 2015. Fish movement through an estuary mouth is related to tidal flow. Estuaries and Coasts (October 2015). DOI:  10.1007/s12237-015-0043-3.

Wetlands Loss in the Pacific Northwest and Salmon Density-Dependence

Less habitat, higher densities of fish, lower foraging success?

As even most school children know (at least, school children in the Pacific Northwest), salmon spend most of their adult lives in the ocean, returning to their natal rivers to spawn; the young then make their way downstream to the ocean and the cycle continues. In recent years, more attention has been paid to the time young salmon spend in transitional estuarine habitats, where they hide from predators and forage on abundant food sources to get ready for life in the big, sometimes-bad ocean. Estuarine wetlands serve as important nursery areas for these young salmon, as they do for other species. As wetlands disappear in Pacific Northwest estuaries, what happens to Chinook salmon foraging performance? A recent analysis of data collected by six studies of juvenile Chinook salmon in nine estuaries with varying degrees of wetland loss addressed this question by examining fish densities, foraging performance, and diets. 

Although the results indicated little to no direct effect of wetland loss on salmon foraging and little effect of salmon density on foraging in estuaries experiencing less than 50% wetland loss, there was a significant negative impact of salmon density on foraging in estuaries with greater than 50% wetland loss. The authors believe that large wetland loss leads to density-dependent effects in which fish are competing for scarcer prey resources, which could negatively affect their growth and survival during this critical ontogenetic window. The study also examined diets in each estuary, and found that most salmon prey depend in some way on tidal wetland habitats, highlighting the vulnerability of salmon prey to loss of these habitats. 

One interesting management implication of this work is that the release of hatchery salmon into systems where wetlands have been lost may negatively affect the remaining wild salmon by exacerbating density-dependent effects of reduced habitat. Rather than supplementing those stocks with hatchery production, a better approach could be wetland restoration. 

Source: David, A. T., C. A. Simenstad, J. R. Cordell, J. D. Toft, C. S. Ellings, A. Gray, and H. B. Berge. 2015. Wetland loss, juvenile salmon foraging performance, and density dependence in Pacific Northwest estuaries. Estuaries and Coasts (November 2015). DOI:  10.1007/s12237-015-0041-5

 Building the Data Infrastructure of the Future

As the need for synthesis in estuarine and coastal science grows, so does the need for a comprehensive data storage and management system

Suppose a scientist wanted to examine trends in PCB loading to East Coast estuaries over the previous four decades. Or synthesize information about soil moisture in the Potomac River watershed. Or compare her findings on abundance and distribution of benthic invertebrates in an Oregon estuary to other, similar studies in the Pacific Northwest. These researchers might conduct internet searches, scour the literature, talk to their colleagues, or ask a Listserv for guidance, but there is no one-stop shopping for such data. 

As synthesis studies and holistic approaches become more valuable, researchers are realizing that data sets – theirs and their colleagues’ – have value outside of their original study. Funders also understand that it is cheaper to store and re-use data than to re-collect it. But there is no single, comprehensive data infrastructure that stores and manages coastal and estuarine data sets. A workshop at the 2013 Coastal and Estuarine Research Federation conference, coupled with case studies of two successful coastal synthesis projects, helped to clarify the need for a coastal and estuarine data infrastructure, and provided guidance on requirements, challenges, and possible paths forward. 

Lessons learned from the case studies, combined with outcomes from the workshop, helped shape recommendations for a proposed coastal and estuarine data infrastructure. Among them:

  • Data providers need incentives to share as well as “credit” for doing so. While there are unsolved legal issues related to data ownership, data collectors need to know they will not be “scooped,” perhaps via an embargo system.
  • Data users require advanced search and browse features, as well as the ability to save and amend searches. This functionality relies on development of good metadata.
  • Community standards for data integration are needed; the current lack thereof creates data “silos” that require tremendous effort to integrate.
  • Paths to data digitization and preservation are needed, so older data can be included in electronic databases and no data will fall prey to turnovers in technology.

Existing data repositories satisfy some of these requirements, and other systems are in development. This paper highlights critical aspects of the path forward, including the recommendations that students should be trained on how to share data and mine large data infrastructure, that professionals from the fields of information and library science, software engineering, computer science, and database management should be part of the process, and that there may be a range of business models for financing. 

Source: Thessen, A. E., B. Fertig, J. C. Jarvis, and A. C. Rhodes. 2015. Data infrastructures for estuarine and coastal ecological syntheses. Estuaries and Coasts (November 2015). DOI:  10.1007/s12237-015-0045-1