Best management practices for coastal inlets

Coastal inlets separate individual barrier islands or barrier spits and adjacent headlands (Hayes and Fitzgerald 2013). Inlets modify longshore transport and store sediment in flood and ebb shoals leading to dynamic adjacent shorelines. For example, 80% to 85% of the beach erosion in Florida can be attributed to inlets (Dean 1991). In some cases, structured inlets are designed to trap sand in a preferred location to minimize interference with navigation and facilitate its removal through dredging. Sound coastal engineering practice requires that this sand be placed on adjacent eroding beaches (NRC 1995) to protect coastal resources. This paper provides a brief overview of coastal inlet management and identifies Best Management Practices (BMPs) intended to balance human needs for inlet navigation with the natural systems adjacent to tidal inlets. Today’s conservation measures, which are a result of considerable monitoring, numerical modeling, and other science-based methods, demonstrate that BMPs improve management of sand resources and reduce impacts associated with tidal inlet dredging. For some inlet conditions, BMPs include use of inlet sediment sinks as cost-effective and eco-friendly sand sources for beach nourishment projects located close to the inlet. For optimal coastal inlet management, the ASBPA Science and Technology Committee recommends the following BMPs and conservation measures: • Limit frequency and duration of impacts, • Follow environmental windows, • Implement regional sediment management, • Use beach-compatible sand, • Conduct pre-, during-, and post-dredging monitoring, • Modify dredging equipment/practices, and • Design rechargeable, low-impact inlet borrow sites.

Holocene glacier fluctuations and environmental changes in subantarctic South Georgia inferred from a sediment record from a coastal inlet

The subantarctic island of South Georgia provides terrestrial and coastal marine records of climate variability, which are crucial for the understanding of the drivers of Holocene climate changes in the subantarctic region. Here we investigate a sediment core (Co1305) from a coastal inlet on South Georgia using elemental, lipid biomarker, diatom, and stable isotope data to infer changes in environmental conditions and to constrain the timing of late-glacial and Holocene glacier fluctuations. Because of the scarcity of terrestrial macrofossils and the presence of redeposited and relict organic matter in the sediments, age control for the record was obtained by compound-specific radiocarbon dating of mostly marine-derived n-C16 fatty acids. A basal till layer recovered in Little Jason Lagoon was likely deposited during an advance of local glaciers during the Antarctic cold reversal. After glacier retreat, an oligotrophic lake occupied the site, which transitioned to a marine inlet around 8.0±0.9 ka because of relative sea-level rise. From 7.0±0.6 to 4.0±0.4 ka, reduced vegetation coverage in the catchment, as well as high siliciclastic input and deposition of ice-rafted debris, indicates glacier advances in the terrestrial catchment and likely in the adjacent fjord. A second, less extensive period of glacier advances occurred in the late Holocene, after 1.8±0.3 ka.

Differential Impacts of Land-Based Sources of Pollution on the Microbiota of Southeast Florida Coral Reefs

ABSTRACT Coral reefs are dynamic ecosystems known for decades to be endangered due, in large part, to anthropogenic impacts from land-based sources of pollution (LBSP). In this study, we utilized an Illumina-based next-generation sequencing approach to characterize prokaryotic and fungal communities from samples collected off the southeast coast of Florida. Water samples from coastal inlet discharges, oceanic outfalls of municipal wastewater treatment plants, treated wastewater effluent before discharge, open ocean samples, and coral tissue samples (mucus and polyps) were characterized to determine the relationships between microbial communities in these matrices and those in reef water and coral tissues. Significant differences in microbial communities were noted among all sample types but varied between sampling areas. Contamination from outfalls was found to be the greatest potential source of LBSP influencing native microbial community structure among all reef samples, although pollution from inlets was also noted. Notably, reef water and coral tissue communities were found to be more greatly impacted by LBSP at southern reefs, which also experienced the most degradation during the course of the study. The results of this study provide new insights into how microbial communities from LBSP can impact coral reefs in southeast Florida and suggest that wastewater outfalls may have a greater influence on the microbial diversity and structure of these reef communities than do contaminants carried in runoff, although the influences of runoff and coastal inlet discharge on coral reefs are still substantial. IMPORTANCE Coral reefs are known to be endangered due to sewage discharge and to runoff of nutrients, pesticides, and other substances associated with anthropogenic activity. Here, we used next-generation sequencing to characterize the microbial communities of potential contaminant sources in order to determine how environmental discharges of microbiota and their genetic material may influence the microbiomes of coral reef communities and coastal receiving waters. Runoff delivered through inlet discharges impacted coral microbial communities, but impacts from oceanic outfalls carrying treated wastewater were greater. Geographic differences in the degree of impact suggest that coral microbiomes may be influenced by the microbiological quality of treated wastewater.