Project: Environmental consequences of expanded recruitment of an ecosystem engineer on a hypoxia-influenced continental shelf

NSF Award Abstract:
Highly productive US West Coast fishery species and marine mammals rely on benthic invertebrate communities for food. However, these communities are changing. This project addresses the potential ecological consequences of a new member to these benthic communities, the ghost shrimp Neotrypaea. In estuaries, Neotrypaea continuously rework the sediment via their burrowing activities. The combination of high shrimp abundances and the effects of burrowing mitigate the impacts of nutrient run-off (natural and human-induced) that can exacerbate low oxygen conditions. However, Neotrypaea are also considered threats to the oyster industry because of their sediment-excavating activities. An expansion of their distribution beyond estuaries may have additional unforeseen consequences for the Dungeness crab fishery (regionally valued at $33-74M/y) as Neotrypaea are both competitors with juveniles and prey for larger Dungeness crab. Thus, new data are needed to determine how offshore benthic communities are being altered by the recruitment of Neotrypaea into new habitats. This study is comparing communities with high and low shrimp abundances to understand their impact on offshore benthic communities. The shrimp’s contributions to oxygen and carbon cycling are being estimated through field measurements. Benthic community assessments are quantifying changes to food resources on the seafloor caused by the presence of these relatively large shrimp. The coastal waters along the Oregon-Washington shelf are commercially valuable, yet they are also subject to growing human-related impacts. Sustainable management requires optimizing extractive, cultural, and recreational activities. The broader impacts of this research include key data for managers, commercial fisheries’ stakeholders and oyster growers that inform decisions regarding ocean-use planning and management of burrowing shrimp. This project is providing research training for three graduate students and two summer undergraduate students. Curriculum development for elementary school students is focused on the ecology of soft-bottom benthos. The ocean sandy/muddy benthos are often unknown to K-12 students on the West Coast who are usually more familiar with intertidal and kelp forest systems.

Changing environmental conditions in shelf waters along the Oregon and Washington coasts and elsewhere have included increasingly frequent and severe hypoxia events, ocean acidification, and warming. These changes have affected biological communities and altered species distributions. An abundant mid-shelf population of the burrowing ghost shrimp, Neotrypaea sp. was documented in shelf waters following the Marine Heat Wave of 2015. Neotrypaea are ecosystem engineers that were previously known to be abundant in intertidal estuary mudflats with an insignificant presence in the open ocean. In estuaries Neotrypaea continuously rework the sediment via their burrowing activities. The shrimp can increase oxygen cycling due to burrow irrigation and reduce impacts of nutrient loading such as low-oxygen conditions. However, enhanced benthic oxygen consumption linked to Neotrypaea sp. beds could have the opposite effect on the shelf by intensifying regional hypoxia. This study is characterizing the environmental conditions associated with the expanded distribution of Neotrypaea using a habitat-suitability modeling approach. Model predictions are being validated through extensive field sampling via box coring and video lander observations. In addition, the benthic samples are documenting changes in the benthic invertebrate communities within the Neotrypaea beds and how this is potentially affecting biological interactions. Analyses of aquatic eddy covariance and of core incubations in shelf areas with and without abundant shrimp are providing estimates of the shrimp’s contribution to benthic oxygen fluxes and organic carbon cycling. These data are being used to quantify the shrimp’s and their burrows’ effects on the overall productivity of the mid-shelf benthos relative to reference areas. How Neotrypaea alter seafloor structure and biogeochemistry need to be characterized to predict the impact of these ecosystem engineers on the food supply for higher trophic levels and fisheries.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.