Responses of Ecological Function of the Ship Shoal Biogeochemical Communities Subjected to Dredging
Project Abstract
Ship Shoal is a large transgressive sand shoal located approximately 10 miles off the central coast of Louisiana. Recently, Ship Shoal became an active dredging site to aid coastal restoration in Louisiana because it contains over three billion cubic meters of high quality sand. The shoal is a highly productive and dynamic benthic habitat that is utilized by a diverse and important assemblage of species, including several federally managed species. The shoal is also spawning habitat for commercially important species such as blue crabs, and other nekton as well. To properly manage dredging activity and retain the critical ecological function of the shoal it is necessary to understand the responses of the shoal ecosystem to the changes in physical and biological drivers induced by dredging. We propose to use a modified Before-After Control Impact (BACI) design to determine the biological, physical, and chemical responses of borrow areas on Ship Shoal compared to control sites. Seasonal and diel samples will be collected over the project period that will bracket the period of dredging. We will use bathymetric and side-scan sonar to map each site prior to and after dredging. During each seasonal sampling period we will use box cores, trawling, long line, gillnets and high resolution sonar imaging to quantify the abundances of benthic infauna and to estimate abundance and observe fine-scale behavior of nekton during the day and at night at both control and dredge sites. We will collect tissue samples from nekton, benthic invertebrates, and all potential primary producers to determine food web structure using stable isotope analyses. We will measure primary production rates of phytobenthos to determine effects of dredging on benthic PP. These data will provide a basis for modeling impacts of dredging on the biological function of Ship Shoal. BOEM has devoted funding through two ongoing projects toward better understanding how dredging pits evolve in Ship Shoal and the potential impacts to infrastructure and/or resources of concern located adjacent to the pits. This new proposed ecology project will build upon the data and resources from current BOEM-funded projects to increase BOEM’s decision making ability regarding the safety and protection of ecological, environmental and cultural resources.
Project Abstract
Ship Shoal is a large transgressive sand shoal located approximately 10 miles off the central coast of Louisiana. Recently, Ship Shoal became an active dredging site to aid coastal restoration in Louisiana because it contains over three billion cubic meters of high quality sand. The shoal is a highly productive and dynamic benthic habitat that is utilized by a diverse and important assemblage of species, including several federally managed species. The shoal is also spawning habitat for commercially important species such as blue crabs, and other nekton as well. To properly manage dredging activity and retain the critical ecological function of the shoal it is necessary to understand the responses of the shoal ecosystem to the changes in physical and biological drivers induced by dredging. We propose to use a modified Before-After Control Impact (BACI) design to determine the biological, physical, and chemical responses of borrow areas on Ship Shoal compared to control sites. Seasonal and diel samples will be collected over the project period that will bracket the period of dredging. We will use bathymetric and side-scan sonar to map each site prior to and after dredging. During each seasonal sampling period we will use box cores, trawling, long line, gillnets and high resolution sonar imaging to quantify the abundances of benthic infauna and to estimate abundance and observe fine-scale behavior of nekton during the day and at night at both control and dredge sites. We will collect tissue samples from nekton, benthic invertebrates, and all potential primary producers to determine food web structure using stable isotope analyses. We will measure primary production rates of phytobenthos to determine effects of dredging on benthic PP. These data will provide a basis for modeling impacts of dredging on the biological function of Ship Shoal. BOEM has devoted funding through two ongoing projects toward better understanding how dredging pits evolve in Ship Shoal and the potential impacts to infrastructure and/or resources of concern located adjacent to the pits. This new proposed ecology project will build upon the data and resources from current BOEM-funded projects to increase BOEM’s decision making ability regarding the safety and protection of ecological, environmental and cultural resources.
The First Cruise: November 2020
The first Ship Shoal cruise set out the morning of November 14, 2020, with sampling spanning over two days and soil incubations to follow:
The first Ship Shoal cruise set out the morning of November 14, 2020, with sampling spanning over two days and soil incubations to follow:
Preliminary results from a randomly selected core incubation following November 2020 sampling cruise