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Wells Beach Station, ME, United States

Vincent R.E.,National Oceanic and Atmospheric Administration | Vincent R.E.,University of New Hampshire | Burdick D.M.,University of New Hampshire | Dionne M.,Wells National Estuarine Research Reserve
Estuaries and Coasts | Year: 2013

Anthropogenic activities in New England salt marshes have altered hydrologic flows in various ways, but unintended consequences from some types of habitat modifications have received little attention. Specifically, ditches have existed on salt marshes for decades, but the effects of these hydrologic alterations are only poorly understood. Ditch-plugging is a more recent methodology used for salt marsh habitat enhancement and mosquito control, but the long-term effects from this management practice are also unclear. The interactions involving marsh surface elevation, soil characteristics, and hydrologic regimes result in feedbacks that regulate the salt marsh self-maintenance process, and these interactions vary with hydrologic modification. Using natural tidal creeks and pools as controls, we examined the effects of ditching and plugging, respectively, on hydrology, surface elevations, and soils. Results showed the most apparent effects of altered hydrology from ditching are prolonged pore-water retention in the rooting zone and significantly lower soil bulk density and mineral content when compared with natural creek habitat. From a management perspective, the important question is whether the combined alterations to physical and biological processes will hinder the marsh's ability to keep pace with increasing rates of sea level rise, especially in more heavily ditched marshes. In contrast, ditch-plugging results in the decoupling of feedback processes that promote salt marsh self-maintenance and in doing so, threatens marsh stability and resilience to climate change. High surface water levels, permanently saturated soils, marsh subsidence, and significantly lower bulk density, carbon storage, soil strength, and redox levels associated with hydrologic alterations from ditch-plugging all support this conclusion. © 2013 Coastal and Estuarine Research Federation.

Bullard S.G.,University of Hartford | Carman M.R.,Woods Hole Oceanographic Institution | Rocha R.M.,Federal University of Parana | Dijkstra J.A.,Wells National Estuarine Research Reserve | Goodin A.M.,Massachusetts College of Liberal Arts
Aquatic Invasions | Year: 2011

Little is known about the ascidian fauna of Pacific Panama. Ascidian surveys were conducted in the southern Gulf of Chiriquí on the Pacific coast of Panama in January 2008 and 2009. Surveys along linear transects at 2-3 m depth (snorkel, 2008) and 5 and 12 m depth (SCUBA, 2009) were conducted at multiple sites within a chain of islands extending out from the mainland. Twelve different ascidian taxa were observed with mean densities of up to ~17 ascidians m -2. The most abundant species was Rhopalaea birkelandi. Two of the most abundant taxa (Ascidia sp., Pyura sp.) appear to represent previously undescribed species. Several species of didemnids were also abundant. Ascidians were most abundant near the coast of the mainland and were less abundant near the islands farthest offshore. These data on Panamanian ascidian communities provide a baseline of local biodiversity against which it will be possible to determine whether the communities change over time, if additional species become introduced to the region, or if native Panamanian species become invasive in other parts of the world. © 2011 The Author(s).

Carman M.R.,Woods Hole Oceanographic Institution | Bullard S.G.,University of Hartford | Rocha R.M.,Federal University of Parana | Lambert G.,University of Washington | And 5 more authors.
Aquatic Invasions | Year: 2011

The Panama Canal region is susceptible to non-native species introductions due to the heavy international shipping traffic through the area. Ascidian introductions are occurring worldwide but little is known about introductions at the Panama Canal. Surveys were conducted in 2002, 2008, and 2009 within the Pacific and Atlantic entrances to the canal. We found a high diversity of ascidians on both sides of the canal, dominated by non-native species; six species occurred at both Pacific and Atlantic Panama sites. This is the first report of Polyandrocarpa anguinea and P. sagamiensis in Atlantic Panama waters and Ascidia incrassata, Ascidia sydneiensis, Botrylloides nigrum, Botryllus planus, Didemnum perlucidum, Diplosoma listerianum, Microcosmus exasperatus, Polyandrocarpa zorritensis, Polyclinum constellatum, Symplegma brakenhielmi, Symplegma rubra, and Trididemnum orbiculatum in Pacific Panama waters. The canal may serve as a major invasion corridor for ascidians and should be monitored over time. © 2011 REABIC.

Griffin P.J.,University of Southern Maine | Theodose T.,University of Southern Maine | Dionne M.,Wells National Estuarine Research Reserve
Wetlands | Year: 2011

Most salt marshes are dominated by graminoids, but patches dominated by a diverse assemblage of perennial forbs, known as forb pannes, occur on marshes in north temperate areas. These pannes and their associated species diversity appear to be highly responsive to anthropogenic change, including climate warming. We mapped all of the forb pannes on a salt marsh in Wells, Maine in order to 1) determine if geospatial features were related to panne location and species composition, and 2) record a baseline to compare with future responses to anthropogenic change. Forb pannes occupied approximately 5% of the high marsh surface, with sizes ranging from 7 m 2 to 5000 m 2. Pannes themselves were clustered at river/creek edges and near pools. Within pannes, species diversity was highest away from pools and the river mouth, and relative abundance of Plantago maritima was related to spatial variables. These results suggest that forb panne distribution and community structure are influenced by spatial variables and reinforce the notion that forb pannes may be used to track salt marsh responses to global change. © 2011 Society of Wetland Scientists.

Vincent R.E.,National Oceanic and Atmospheric Administration | Vincent R.E.,University of New Hampshire | Burdick D.M.,University of New Hampshire | Dionne M.,Wells National Estuarine Research Reserve
Estuaries and Coasts | Year: 2014

Salt marsh plant communities are regulated by feedback processes involving hydrologic regimes, disturbance, and marsh physical characteristics, and as expected differ among habitat types. Using three barrier beach salt marshes along the Gulf of Maine, we examined the effects of ditching and ditch-plugging on plant characteristics by means of comparisons to natural creek and pool habitats. Results indicated that ditch and creek habitats were similar in terms of species richness and diversity of emergent vascular plants, but cover and biomass were significantly higher in habitat adjacent to creeks. Plant composition in ditch habitat was distinguished by the higher percentage of forb species (associated with poor drainage), while the proportion of tall-form Spartina alterniflora was much higher in creek habitat (associated with sloping banks of creeks). These results are indicative of differences in hydrologic and disturbance regimes that can influence competitive and facilitative interactions, habitat structure, and heterogeneity. Results for pool comparisons indicated that plant characteristics were significantly different between ditch-plug and natural pools. Species richness, diversity, and biomass were significantly lower in ditch-plug habitat compared with all other habitats, and plant cover averaged only 30 % in habitat adjacent to ditch-plugs, which was significantly lower than all other habitats. These differences have ecological implications in terms of habitat structure and function of ditch-plug habitat. In addition, increased stress leading to plant dieback due to ditch-plugging has resulted in subsidence that can decrease the stability of ditch-plug habitat and expedite the loss of salt marsh habitat, especially with rising sea levels. © 2013 Coastal and Estuarine Research Federation.

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