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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 April

Contents

Sand and Sandy
Fishing for Data
Rising Seas Threaten Arctic Native Heritage Site
Seeking Clarity on Water Turbidity in the Sacramento-San Joaquin River Delta

Sand and Sandy

Lessons from Hurricane Sandy’s impact on sediment transport in a New Jersey back-barrier estuary

Large storms can wreak havoc on barrier islands, redistributing sediment, altering shorelines, and causing new breaches. Sometimes a barrier island’s storm-induced loss of sediment is the estuary’s gain, as sediment originating on the island is deposited in the adjacent water. With the increasing storms that are predicted to result from climate change, managers would benefit from a better understanding of these island-back bay linkages. A dramatic opportunity to study this link came with Hurricane Sandy in October 2012. Researchers were already engaged in an extensive monitoring program in Barnegat Bay, NJ, examining trends in water quality, hydrology, and bathymetry. This pre-existing data set and monitoring infrastructure offered the rare opportunity to compare the system before and after the massive storm made landfall about 10 km from the study site. The research team was particularly interested in the coupling of sediment dynamics between the estuary and the barrier island.

The storm led to significant changes on the barrier island, including shoreline retreat and decreases in dune height. A great deal of sediment was lost, particularly from undeveloped areas where there were broader beaches and bigger dunes and therefore greater sediment availability. Two new breaches formed in the barrier island, and although the causes of these breaches are complex, they both occurred from the oceanic side of the island in narrower stretches of the island. The estuary experienced a limited net gain of sediment: sediment deposition tended to occur near barrier island breaches and in the back barrier shoreline of developed areas (near deeper estuarine sites where dredging had occurred). This type of study can help improve our understanding of the response of barrier island/estuarine systems to storms, thus informing efforts to adapt to climate change.

Source: Miselis, J. L., B. D. Andrews, R. S. Nicholson, Z. Define, N. K. Ganju, and A. Navoy. 2015. Evolution of Mid-Atlantic coastal and back-barrier estuary environments in response to a hurricane: implications for barrier-estuary connectivity. Estuaries and Coasts (December 2015). DOI: 10.1007/s12237-015-0057-x.

Other resources: Mapping, Measuring, and Modeling to Understand Water-Quality Dynamics in Barnegat Bay-Little Egg Harbor Estuary, New Jersey. http://soundwaves.usgs.gov/2013/02/

Hurricane Sandy Disrupts USGS study of the Barnegat Bay-Little Egg Harbor Estuary in New Jersey, Provides Additional Research Opportunities. http://soundwaves.usgs.gov/2013/02/fieldwork2.html

Fishing for Data

Can fishery data be used to identify effects of anthropogenic stresses and environmental variability on nekton? 

In some ways commercial fishing is similar to a scientific survey: both involve collection of specimens using standardized gear, usually in roughly the same areas or during the same seasons (or both) from year to year. Using a metric like catch per unit effort, both kinds of collections can be compared among places or times. Of course, there are also significant differences between fishing for fish and fishing for data, particularly the fact that fishers want to make sure they actually catch their target, and will adjust their methods appropriately. Given the importance of environmental monitoring, could the nekton collections carried out by fishermen be turned into useful data for evaluating ecosystems? A study in Venice lagoon, Italy, aimed to provide some insight.

Investigators wanted to determine whether anthropogenic stressors and environmental variability had an effect on nekton species richness and biomass in the lagoon using data from the artisanal fyke net fishery there. They examined catches in the fishery in five areas within the lagoon over two time periods (2001-2003 and 2009-2013), and analyzed changes in composition and biomass of target and non-target species as well as of various ecological and diet species groups. They also monitored parameters related to anthropogenic pressures on the system (ranging from boat traffic to seagrass habitat loss to hypoxia events) and environmental conditions (e.g., percent area covered by salt marsh, salinity, turbidity). 

Nektonic biomass measured in the artisanal fishery was significantly correlated with parameters describing anthropogenic pressures and environmental variability, whereas species richness did not show a significant response. Both nektonic biomass and species richness showed distinct temporal trends across seasons and years. The results also suggest that the impact of the fishery itself on both species richness and biomass was negligible. These results indicate that species richness appears to be less appropriate than biomass as an indicator of the ecological status of coastal waters. Further, the authors conclude, the artisanal fishery appears to be sustainable at the present level of effort, as it is not having a significant impact on nekton species richness or biomass. 

Source: Zucchetta, M., L. Scapin, F. Cavraro, F. Pranovi, A. Franco, and P. Franzoi. 2016. Can the effects of anthropogenic pressures and environmental variability on nekton fauna be detected in fishery data? Insights from the monitoring of the artisanal fishery within the Venice Lagoon. Estuaries and Coasts (January 2016). DOI: 10.1007/s12237-015-0064-y. 

Rising Seas Threaten Arctic Native Heritage Site

Trouble may be ahead for potential UNESCO World Heritage site 

As global climate change has become not just a future threat but a current reality, an increasing amount of attention is being focused on the vulnerability of coastal resources to rising seas, more frequent and more intense storms, and accompanying enhanced erosion. Little work of this kind has been done in the coastal Arctic, despite the fact that warming there exceeds the global mean and erosion has intensified along Arctic shores in recent decades. Modern settlements and important cultural heritage sites dot the Arctic’s shores, all of which could be vulnerable to these threats. One recent study examined the vulnerability of Simpson Point, a gravelly spit on Herschel Island in the Beaufort Sea that is home to a historic whaling settlement and many archaeological sites. An important cultural site for the native Inuvialuit, the island is being considered for designation as a UNESCO World Heritage site because of its cultural and biological value. The investigators examined historical aerial photography to map the shoreline of the area for several time periods between 1951 and 2011, and used linear regressions to project location of the coastline 20 and 50 years into the future. 

On average the shoreline retreated across the entire study area, although the rates of retreat varied by location and time period. Overall rates of erosion were highest in the most recent time period (2000-2011). Higher shoreline erosion rates were generally correlated with wave exposure, and higher ice content in the soil. Projections of future shoreline configurations revealed that although some areas of Simpson Point might accrete, the entire spit, including the critical archaeological sites, will be highly vulnerable to future flooding. Although structural (sea walls, groins) and non-structural (relocation of sites, beach nourishment) approaches to protecting the sites could be considered, the authors note that many structural measures will not be economically feasible due to the remoteness of the location. Any approaches to preservation should be planned in close consultation with the Inuvialuit, respecting their attitudes toward land use and the appropriate treatment of cultural sites. 

Source: Radosavljevic, B., H. Lantuit, W. Pollard, P. Overduin, N. Couture, T. Sachs, V. Helm, and M. Fritz. 2015. Erosion and flooding – threats to coastal infrastructure in the Arctic: a case study from Herschel Island, Yukon Territory, Canada. Estuaries and Coasts (November 2015). DOI: 10.1007/s12237-015-0046-0.

Seeking Clarity on Water Turbidity in the Sacramento-San Joaquin River Delta

Waters seem to be getting less turbid in the delta. What role has SAV played?

Submerged aquatic vegetation generally needs clear water to thrive, but it can also enhance water clarity by slowing water movement and allowing suspended sediments to settle out of the water column. This feedback loop can result in even greater growth of SAV. Of course, reduced sediment or nutrient loads and growth of filter-feeder populations can also increase water clarity. The Sacramento-San Joaquin River Delta is one place where water turbidity has declined in recent decades, while sediment loading has been curtailed and SAV has been on the rise. Can the impact of these factors be teased apart? A team of researchers used long-term suspended sediment and turbidity monitoring data and remote sensing imagery of SAV beds to try to find out.

Results revealed a significant decline in turbidity from 1975 to 2008, as well as a decreasing trend in sediment load and an increasing trend in SAV bed extent. Using statistical techniques, the investigators were able to remove the sediment supply signal from the downward turbidity trend. When they did this the trend remained negative, suggesting that another factor was at work. Stations with high rates of SAV expansion had more significant decreases in turbidity, suggesting that SAV is at least partially responsible for the decline. Overall, the study estimates that 21-70% of the declining turbidity trend is due to SAV expansion.

While managers often strive to protect and even restore lost SAV beds in many systems, here the goals are not so clear. For example, juvenile delta smelt, an endangered species, are adapted to more turbid waters that provide protection to feeding juveniles. In addition, SAV species in this system are mostly invasive, and the beds appear to provide habitat for other invasives like largemouth bass.

Source: Hestir, E. L., D. H. Schoellhamer, J. Greenberg, T. Morgan-King, and S. L. Ustin. 2015. The effect of submerged aquatic vegetation expansion on a declining turbidity trend in the Sacramento-San Joaquin River Delta. Estuaries and Coasts (December 2015). DOI:  10.1007/s12237-015-0055-z.