Showing 1 - 4 of 4 Items
Functional redundancy of a non-native foundation species (eelgrass, Zostera japonica) across intertidal stress gradients
Date: 2023-01-01
Creator: S. Maria Garcia
Access: Open access
- Non-native species foundation species can alter ecosystems in both positive and negative ways. The creation of habitat can be beneficial to native species when they provide a limiting resource or in a stressful environment. Yet this creation of habitat can also be detrimental by replacing native species and/or facilitating the presence of more non-native species. In Willapa Bay, WA, a non-native foundation species, Zostera japonica, co-exists with the native foundation species Zostera marina. Zostera japonica persists at the higher intertidal in monocultures, the two species overlap in the mid intertidal, and Z. marina persists in monocultures in the low intertidal. Epifaunal invertebrates, the organisms that live on eelgrass blades, connect eelgrass to higher trophic levels. Through a series of transplants and removals, I used this zonation pattern to ask if the two species can fulfill a similar functional role in respect to epifaunal invertebrates (functional redundancy), and if this was due to the identity of the foundation species or a response to the stress gradient of the intertidal. My results suggest that the epifaunal invertebrate community is responding more to the physiological stress gradient, and the functional redundancy of the two species depends on the location they are found. Z. japonica is expanding the range of vegetated habitat into to the physiologically stressful high zone, which supports a different community. This experiment highlights that the impacts of non- native species are highly localized and that abiotic and biotic factors are important to trophic interactions.
Eelgrass meadow structure drives epifaunal community composition more than temperature during a Marine Heat Wave in the Gulf of Maine This record is embargoed.
- Embargo End Date: 2029-05-16
Date: 2024-01-01
Creator: Nicholas Takaki Tienhui Yoong
Access: Embargoed
Freezing temperatures drive functional trait clustering more than habitat structure in eelgrass communities in the Gulf of Maine This record is embargoed.
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Bridget Marjorie Patterson
Access: Embargoed
Impacts of eelgrass (Zostera marina) on pore-water sulfide concentrations in intertidal sediments of Casco Bay, Maine
Date: 2016-05-01
Creator: Sabine Y Berzins
Access: Open access
- Eelgrass (Zostera marina) is a perennial seagrass that provides many vital ecosystem services including stabilizing sediments, maintaining water clarity, and providing complex habitat in the intertidal and shallow subtidal coastline. Historically, Maine supported dense eelgrass beds in shallow waters surrounding islands and along the coastal mainland. However, in 2012, high population densities of European green crabs (Carcinus maenas), which physically disturb and remove eelgrass as they forage, were correlated with widespread eelgrass declines. Over 55% of the area of eelgrass in Casco Bay was lost, mainly between 2012 and 2014. Eelgrass typically grows in low-oxygen sediments that produce a chemically reducing environment. Sulfate-reducing bacteria in these reduced sediments produce hydrogen sulfide, a toxin that can intrude into eelgrass tissues and impair the plants’ ability to photosynthesize. When eelgrass is not present, sulfide can build up in the pore-water. When eelgrass is present, it can oxygenate the sediments through its roots, thereby preventing the intrusion and buildup of toxic hydrogen sulfide. However, if the substrate is de-vegetated, oxygen levels drop as sedimentary organic matter is decomposed, and the accumulation of sulfides to harmful concentrations in the pore-water may make recolonization of eelgrass difficult or perhaps impossible even in the absence of green crabs. In an effort to monitor characteristics of Casco Bay eelgrass beds and determine spatially where eelgrass may be more likely to recover, four Casco Bay sites with varying degrees of vegetation loss were sampled in 2015 for pore-water sulfide concentration, sediment carbon and nitrogen content, and sediment grain size analysis. Measurements of sulfide concentrations showed correlations with the timing of eelgrass loss, such that vegetated sites had low pore-water sulfide concentrations and sites that had been de-vegetated for longer periods of time had high sulfide concentrations. Carbon and nitrogen content in the sediment was higher at de-vegetated sites, likely due to a higher percentage of finer sediments at those locations. Coarser sediments were more highly vegetated than finer sediments, perhaps displaying a preference of green crabs to forage in finer sediments. Catastrophic loss of eelgrass in Casco Bay has likely led to differences in sulfide levels, carbon and nitrogen content in the sediment, and grain size distribution, depending on degree of vegetation. Eelgrass restoration in Casco Bay will likely be limited by high pore-water sulfide concentrations.