The Potential for Created Oyster Shell Reefs as a Sustainable Shoreline Protection Strategy in Louisiana

Coastal protection remains a global priority. Protection and maintenance of shoreline integrity is often a goal of many coastal protection programs. Typically, shorelines are protected by armoring them with hard, non‐native, and nonsustainable materials such as limestone. This study investigated the potential shoreline protection role of created, three‐dimensional Eastern oyster (Crassostrea virginica) shell reefs fringing eroding marsh shorelines in Louisiana. Experimental reefs (25 × 1.0 × 0.7 m; intertidal) were created in June 2002 at both high and low wave energy shorelines. Six 25‐m study sites (three cultched and three control noncultched) were established at each shoreline in June 2002, for a total of 12 sites. Shoreline retreat was reduced in cultched low‐energy shorelines as compared to the control low‐energy shorelines (analysis of variance; p < 0.001) but was not significantly different between cultched and noncultched sites in high‐energy environments. Spat set increased from 0.5 ± 0.1 spat/shell in July 2002 to a peak of 9.5 ± 0.4 spat/shell in October 2002. On average, oyster spat grew at a rate of 0.05 mm/day through the duration of the study. Recruitment and growth rates of oyster spat suggested potential reef sustainability over time. Small fringing reefs may be a useful tool in protecting shorelines in low‐energy environments. However, their usefulness may be limited in high‐energy environments.     

Rapid Seed Bank Development in Restored Tidal Freshwater Wetlands

Studies of seed bank development have rarely been included in evaluations of wetland restoration. We compared the seed bank of a recently restored tidal freshwater marsh in Washington, D.C., Kingman Marsh, with seed banks of another restored site (Kenilworth Marsh) and two reference marshes (Dueling Creek and Patuxent Marsh). The density and richness of emerging seedlings from Kingman Marsh seed bank samples increased from less than 4 seedlings and 2 taxa/90-cm² sample in 2000 (the year of restoration) to more than 130 seedlings and 10 taxa/90-cm² sample in 2003. The most important seed bank taxa at Kingman Marsh included Cyperus spp., Juncus spp., Lindernia dubia , Ludwigia palustris , and the non-native Lythrum salicaria . These taxa are not abundant in most mid-Atlantic tidal freshwater marshes but are almost identical to those described for a created tidal freshwater wetland in New Jersey. Seed banks of both the restored sites contained few seeds of several important species found at the reference sites. Flooding had a significant negative effect on emerging seedling density and taxa density, suggesting that slight decreases in soil elevation in restored wetlands will dramatically decrease recruitment from the seed bank. Because seed banks integrate processes affecting growth and reproduction of standing vegetation, we suggest that seed banks are a useful metric of wetland restoration success and urge that seed bank studies be incorporated into monitoring programs for restored wetlands.     

Assessing Impacts of Hydropattern Restoration of an Overdrained Wetland on Soil Nutrients, Vegetation and Fire

Restoring hydrology to overdrained wetlands can facilitate restoration of degraded ecosystems. In the northern Everglades, the Rotenberger Wildlife Management Area (RWMA) became a rain-driven system as historic overland inflows were redirected. Consequently, the soil experienced severe drying, resulting in frequent muck fires, oxidation and a shift in vegetation composition. In July 2001, the RWMA hydropattern restoration began utilizing discharge from Stormwater Treatment Area 5 (STA-5), a constructed wetland. As a result, predischarge hydroperiods averaging 124 days increased to an average of 183 days. Soil total phosphorus (TP) concentrations in the topsoil layer did not significantly change from predischarge (637 mg/kg) to postdischarge (633 mg/kg) concentrations. Muck fires appear to be the catalyst for rapid alterations in the bioavailability and solubility of P. Prior to muck fires, soil P pools were 88% organic P and 12% inorganic P, shifting to 49% organic P and 51% inorganic P measured after a muck fire. Sawgrass ( Cladium jamaicense , OBL) and Cattail ( Typha domingensis , OBL) cover approximately 75% of the RWMA area as dominant or codominant species. Predischarge vegetation community composition documented obligate (OBL) and facultative wetland (FACW) species, each composing 46% of all species surveyed. Postdischarge vegetation compositions shifted to 59% OBL and 39% FACW species. In addition, there were significant elevations in tissue nutrient concentrations, TP, and total nitrogen, between pre- and postdischarge samples. An adaptive management approach to inflow and outflow operations will be an important part of successful wetland restoration.     

Ecological consequences of altered hydrological regimes in fragmented ecosystems in southern Australia: Impacts and possible management responses

Abstract Although the potential impacts of rising water tables and secondary salinization on agricultural land in southern Australia have been recognized for some time, it is only recently that the impacts on native vegetation have been considered. Despite the likely extent and severity of the problem, no comprehensive approach to assessing the impact of salinity upon native vegetation has been attempted to date. In the present paper, we discuss the causes and impacts of rising water tables and dryland salinity, assess the levels of risk in different ecosystem types and consider the possibilities for the maintenance of biodiversity and ecosystem function in vegetation at risk. We examine the salinity risk to woodland vegetation in the Western Australian (WA) wheatbelt, and consider both broad‐scale context and finer‐scale variation within individual patches of vegetation. From this information, we develop a set of conceptual models of the potential impacts of shallow saline water tables on ecosystem structure and processes in remnant vegetation in agricultural areas, particularly in the WA wheatbelt. First, we suggest that fine‐scale variability in surface topography and soil characteristics may play an important role in limiting the impacts of rising saline water tables. The outcome will depend on the interaction of the heterogeneity of the impact, species distribution in relation to small‐scale environmental heterogeneity and variation in species response to hydrological change. Second, we suggest that shallow saline water tables can be considered to cause an ‘edge effect’, which moves inwards from the edge of remnants of native vegetation. Finally, we consider how saline surface flows exacerbate the effects of shallow saline water tables and hasten vegetation decline in remnant areas. We put these models forward as hypotheses to be tested in different situations. We contrast the situation of secondary salinization in Australian vegetation with that of naturally saline systems in Australia and elsewhere, and suggest that these systems may provide important signposts toward developing management approaches for vegetation at risk. In conclusion, we consider the need to set priorities for the protection and restoration of natural vegetation at risk from altered hydrology, based on an assessment of relative threat and probability of persistence or recovery. We highlight the urgency for action that protects native vegetation from the increasing risks of rising water tables.     

Waterbirds as indicators of ecosystem health in the coastal marine habitats of southern Florida: 1. Selection and justification for a suite of indicator species

The coastal marine environment is currently under threat from many anthropogenic pressures that were identified by the MARES project. Indicators of ecosystem health are needed so that targets can be set to guide protection and restoration efforts. Species of birds that are dependent on coastal habitats are ubiquitous along the coasts of southern Florida. Generally referred to as waterbirds, these species, although not all taxonomically related, share a common dependency on the marine environment for food, nesting habitat, or both. A suite of waterbirds was selected based on their perceived sensitivity to pressures in multiple coastal habitat types. The list of species was refined on the basis of a review of life history for characteristics that might make the species particularly vulnerable. Each selected species was then evaluated for sensitivity to the identified pressures using a hierarchical assessment that took into account the sensitivity, severity, and the temporal and spatial scales of the indicator to the given pressures. The selected suite of indicators was collectively sensitive to all the pressures except one.     

A new analytical method for wildlife habitat conservation planning on a city scale using the classification of physiologically homogeneous areas

Kyoto has a tradition of positively protecting scenic landscapes. However, a question has arisen about the effectiveness of the present legislative system on biodiversity conservation because most laws aim to essentially preserve the aesthetic value of the landscape. It is necessary to identify gaps in the present conservation system to develop an effective conservation policy for the city. The authors propose a practical method of analysis for wildlife habitat conservation planning without wildlife distribution information, which is the usual situation in many cities, and discuss the usefulness and limitations of the method by applying it to Kyoto. The proposed method relies on both of the following two assumptions: (1) the physical properties of the environment are closely related to the potential vegetation communities and (2) the conservation or restoration of rare or extinct vegetation communities ensures diverse wildlife habitats, contributing to biodiversity enhancement in a region. Thus it should be deemed a supplementary analysis to other types of analyses employing endangered, umbrella and/or flagship species in the planning process. A unique aspect of the method is to evaluate land potential, which is important for long-term conservation planning and the determination of target vegetation communities in restoration projects. In Kyoto, this revealed that the candidates for vegetation communities, prioritized for conservation and restoration, were appropriate. Moreover, identifying physiotopes corresponding with none of the existing vegetation communities was another advantage providing useful information for restoration planning. However, it was considered that a filtering process, with auxiliary information about the trend of vegetation communities over time, was necessary after applying the proposed method.     

Ecosystem response to changes in water level of Lake Ontario marshes: lessons from the restoration of Cootes Paradise Marsh

A general understanding of how aquatic vegetation responds to water-level fluctuations is needed to guide restoration of Great Lakes coastal wetlands because inter-annual and seasonal variations often confound effects of costly remedial actions. In 1997, common carp (Cyprinus carpio) was removed from Cootes Paradise Marsh (L. Ontario) to reduce sediment resuspension and bioturbation, and thus regenerate marsh plants that had declined dramatically since the 1930s. Data from 1934 to 1993 were re-assembled from the literature to relate percentage cover of emergent vegetation to mean summer water level. A non-linear regression equation explained close to 90% of the variation compared with 80% for a non-linear equation, and this trend was confirmed for the dominant species, Typha latifolia. A modest recovery of emergent vegetation in 1999 following carp exclusion could have been predicted from declining water level alone, without invoking any effects of the biomanipulation. An unusually cool spring in 1997 delayed the migration of spawning planktivores into the marsh. This resulted in a grazer-mediated clear-water phase that coincided with a resurgence of the submersed aquatic vegetation (SAV) community in 1997, which declined again in 1999 when low water levels occurred. Even though decrease in water level was significantly related to increased suspended solids and greater light attenuation, light conditions appeared to have been adequate in marsh embayments to support SAV growth, according to a published relationship between maximum depth of SAV colonization and light extinction coefficient. I suggest that wave disturbance and propagule burial associated with shallow water depths may have been the main reasons for the decline of the SAV in 1999 and 2000.     

Ichthyofaunal utilization of newly-created versus natural salt marsh creeks in Mission Bay,CA

Loss of wetland habitat has proceeded at an alarmingrate in southern California, and increasingly marshrestoration and creation are being used to mitigatethese losses. As part of an effort to evaluatefunctional equivalence of created systems, theichthyofaunal assemblages in a created and adjacentnatural marsh in Mission Bay, San Diego, Californiawere compared. Fishes trapped in both marshes includedFundulus parvipinnis, Gillichthysmirabilis, Acanthogobius flavimanus, Ctenogobius sagittula, Atherinops affinis, andMugil cephalus. Fundulus parvipinniswasnumerically dominant in both systems, representing onaverage 69% of all fishes trapped in the createdmarsh and 65% of all fishes trapped in the naturalmarsh. Gillichthys mirabiliswas the second-mostabundant species, representing on average 31% of allfishes trapped in the created marsh and 28% of allfishes trapped in the natural marsh. Species richnessand dominance measures were similar between the twosystems, while abundances were higher in the naturalrelative to the created marsh. The size-structure ofF. parvipinnisand G. mirabilisdifferedbetween the created and natural marsh creeks, with thecreated marsh populations being skewed towards largersize classes. These size differences are believed toarise from differences in creek morphology between thecreated and natural systems, and potentially affectboth predators and prey of these species in the marsh.Mark-release-recapture revealed considerable marshfidelity, with as many as 35% of the F.parvipinnistagged in a marsh being recovered one daylater in the same marsh. Stable isotope analyses ofF. parvipinnisrevealed similar ¹⁵Nand ³⁴S values between marshes; howeverthere was a consistent enrichment in ¹³C (>3per mil) in tissues of F. parvipinnisfrom thecreated marsh, supporting the high marsh fidelitysuggested by tagging results. This first publisheddocumentation of the Mission Bay marsh resident fishessuggests that the created marsh ichthyofaunalassemblage was distinct in density and size structurefrom the adjacent natural marsh, and provides lessonsfor future restoration efforts.