RESUMEN
This study aims to characterize the value associated with nature-based recreational opportunities and identify estuarine attributes most valued by users. With the National Ecosystem Service Classification System as a framework, we assessed the relationship between recreational beneficiary subclasses and ecological end-products available to beneficiaries in Tillamook Bay, OR, and Tampa Bay, FL estuaries. We used the InVEST recreation model to assess the spatial distribution and intensity of recreation in both estuaries, then inform site selection in subsequent analyses. We evaluated photo content and collected observational data at sites with the highest utilization. Surveys of location attributes helped determine the availability of ecosystem service ecological end-products. Ordination techniques were employed to evaluate similarities in natural and human-made attributes across stations and establish groups of stations that could offer comparable recreational experiences. Recreational 'experiencers and viewers' were the dominant beneficiary group, as they took the most photos and were most often encountered during passive onsite observations. Composite features (e.g. viewscapes) were the predominant ecological end-products. Counter to hypothesized outcomes, there was no detectable difference in the number of recreational beneficiaries predicted between estuaries after accounting for site-scale variability. Locations with multiple natural and human-made attributes, including access points, had more recreational users. Onsite observations also revealed a potential need for more safe and equitable access options in high-use locations. Findings highlight the importance of recreational 'experiencers and viewers' valuing habitat mosaics, even across vastly different geographical settings. This exploration of how humans derive well-being from coastal landscapes is crucial to ecosystem-based management.
RESUMEN
Estuaries serve as important nurseries for many recreationally and commercially harvested fisheries species. Recent conceptual approaches (i.e., seascape) for assessing the value of estuaries to fisheries have advocated for complex habitat-scale assessments that integrate multiple life-history responses (e.g., abundance, growth, reproduction) and ecological processes across heterogeneous landscapes. Although ecologically compelling, implementing seascape approaches may not be feasible for resource-limited management agencies. In such cases, we propose that resource managers can enhance the identification of fishery-important estuarine habitats by integrating attainable aspects of the seascape approach into a more traditional single response (e.g., abundance) model. Using Dungeness crab (Cancer magister) as a case study, we applied a spatially-explicit hybrid approach to assess the relative contribution of different estuarine habitats to that important fishery species within three Oregon estuaries (Tillamook, Yaquina, and Alsea bays). We measured the abundance of juvenile C. magister from low-tide trawls in estuarine channels and the mosaic of habitat characteristics within defined home-range distances for the crabs. After identifying and reducing strong intercorrelations among habitat variable data, we developed a best-fit model that associated crab abundance with the most influential habitat variables. We found that lower-estuary side channels supported the highest abundance of juvenile crabs; furthermore, crab abundance was positively associated with high salinity and burrowing shrimp (Upogebia pugettensis) density on adjacent unvegetated tidal flats. This hybrid method produced a habitat-specific model that better predicted juvenile C. magister abundance than did a model based on generalized habitat categories.
RESUMEN
Habitat suitability models are useful to estimate the potential distribution of a species of interest, particularly in the case of infaunal bivalves. Sampling for these bivalves is time- and cost-intensive, which is increasingly difficult for organizations or agencies that are limited by personnel and funds. Consequently, we developed a framework to identify suitable bivalve habitat in estuaries (FISBHE) - a habitat suitability index (HSI) modeling framework for NE Pacific estuaries that was parameterized with published natural-hi story information and existing habitat datasets, without requiring extensive field sampling of bivalves. Spatially explicit, rule-based habitat suitability models were constructed in a GIS for five species of bay-clams (Clinocardium nuttallii, My a arenaria, Tresus capax, Saxidomus gigantea, and Leukoma staminea) that are popular targets for recreational and commercial harvest in estuaries of the U.S. Pacific Northwest. Habitat rasters were produced for Yaquina and Tillamook estuaries (Oregon, USA) using environmental data (bathymetric depth, sediment % silt-clay, wet-season salinity, and burrowing shrimp presence/absence) from multiple studies (1953-2015). These habitat rasters then served as inputs in the final model which produced HSI classes ranging from 0-4 (lowest to highest suitability), dependent upon the number of habitat variables that fell within the sensitivity limits for each species of bay-clam. The models were tested with validation analyses and bay-clam occurrence data (reported in benthic community studies, 1996-2012) within each HSI class; logistic regression and Kendall's correlation coefficient both showed correspondence between predicted HSI classes and bay-clam presence/absence. Results also showed that the greatest presence probabilities occurred within habitats of highest predicted suitability, with the exception of M. arenaria in Tillamook Bay. The advantage of FISBHE is that disparate, independent sets of existing data are sufficient to parameterize the models, as well as produce and validate maps of habitat suitability. This approach can be transferred to data-poor systems with modest investment, which can be useful for prioritizing estuarine land-use decisions and could be used to estimate the vulnerability of this valued ecosystem good to changes in habitat quality and distribution.
RESUMEN
Nutrient over-enrichment can produce adverse ecological effects within coastal ecosystems and negatively impact the production of ecosystem goods and services. In small estuaries of the U.S. Pacific Northwest, seasonal blooms of green macroalgae (GMA; Family Ulvaceae) are primarily associated with natural nutrient input, rather than anthropogenic sources. This provided us a unique opportunity to investigate the effects of naturally-stimulated macroalgal blooms on intertidal bivalves. Clinocardium nuttallii (heart cockles) are an important species for shellfisheries in the region. In summer population surveys, we found that cockles emerged from the sediment with greater frequency as GMA biomass increased. Experimental manipulation of GMA biomass in the field showed that GMA elicited emergence, evoked above-ground lateral movement, inhibited shell growth, and increased mortality (by 34.0 ± 15.2%) in cockles. Laboratory experiments revealed that the interaction of a weighted barrier at the sediment surface and GMA presence elicited rapid emergence among cockles. Risk assessment of the emergence response in cockles showed that the in situ emergent population experienced 11.0 ± 8.0% mortality due to gull predation, while laboratory exposure to elevated temperatures (≥34 °C) slowed valve-closure, inhibited reburial, and increased mortality, which could have translated to 7.1 ± 1.5% in situ mortality. We found that cockles avoided mortality due to burial below GMA mats by emerging from the sediment, but that behavior consequently put them at risk of mortality due to heat stress or gull predation. Regardless of nutrient source, our research showed that GMA blooms pose a threat to the survival of intertidal bivalves.