Predicting Carbon and Nutrient Transformations in Tidal Freshwater Wetlands of the Hudson River

The exchange of water between the main channel of the tidal freshwater Hudson River and its tidal wetlands is a large proportion of the whole-river water volume and causes large changes in concentrations of some dissolved and suspended constituents. Ten representative wetlands were assessed for their ability to alter quantities of inorganic nutrients, suspended particles, dissolved organic carbon (DOC), and dissolved oxygen during tidal exchange. The majority of sites acted as sinks for oxygen and nitrate and as sources of DOC. For other variables such as phosphate and pigments, individual wetlands varied broadly in both the direction and magnitude of change. For some variables (oxygen, DOC) we found mechanistically plausible predictors for the magnitude of alteration. The proportional coverage of submerged vegetation or intertidal marsh graminoid vegetation was related to the degree of change in oxygen and DOC. For most cases, however, we did not find strong predictors and we attribute this to the spatial positioning of “hot spots” or redundancy in the processes actually responsible for the transformation. Our ability to predict ecosystem performance from whole-ecosystem attributes may be impeded by lack of consideration of within-system spatial contingencies or lack of knowledge of which process is actually responsible for the observed alteration in material flux.     

Multi-Scale Controls on Water Quality Effects of Submerged Aquatic Vegetation in the Tidal Freshwater Hudson River

Patches of submerged vegetation can be important sites of primary production and habitat for organisms in many aquatic ecosystems. In the tidal freshwater Hudson River they make up about 6% of the river bottom area. Direct sampling of water masses passing through patches of vegetation and week-long continuous monitoring of water characteristics were used to determine plant effects on dissolved oxygen and suspended sediments. Vegetated areas could have dissolved oxygen concentrations substantially higher than in the main channel and suspended sediments and turbidity were frequently higher in vegetated areas. Patches of Vallisneria americana had variable capacity to maintain super-saturated oxygen concentrations; patch size accounted for some of the variability whereas larger-scale differences in main-channel influent water also contributed. Differences in turbidity among sites were harder to account for; width of plant beds and abundance of neighboring vegetated areas contributed weakly to predictions of local turbidity. Functional heterogeneity within ecosystems is common and attempts to explain variability may require understanding different controlling factors for different functions and appreciating that factors operate at multiple scales.     

Processes Contributing to Resilience of Coastal Wetlands to Sea-Level Rise

The objectives of this study were to identify processes that contribute to resilience of coastal wetlands subject to rising sea levels and to determine whether the relative contribution of these processes varies across different wetland community types. We assessed the resilience of wetlands to sea-level rise along a transitional gradient from tidal freshwater forested wetland (TFFW) to marsh by measuring processes controlling wetland elevation. We found that, over 5 years of measurement, TFFWs were resilient, although some marginally, and oligohaline marshes exhibited robust resilience to sea-level rise. We identified fundamental differences in how resilience is maintained across wetland community types, which have important implications for management activities that aim to restore or conserve resilient systems. We showed that the relative importance of surface and subsurface processes in controlling wetland surface elevation change differed between TFFWs and oligohaline marshes. The marshes had significantly higher rates of surface accretion than the TFFWs, and in the marshes, surface accretion was the primary contributor to elevation change. In contrast, elevation change in TFFWs was more heavily influenced by subsurface processes, such as root zone expansion or compaction, which played an important role in determining resilience of TFFWs to rising sea level. When root zone contributions were removed statistically from comparisons between relative sea-level rise and surface elevation change, sites that previously had elevation rate deficits showed a surplus. Therefore, assessments of wetland resilience that do not include subsurface processes will likely misjudge vulnerability to sea-level rise.     

The ecology of freshwater wrack along natural and engineered Hudson River shorelines

Organic matter that is washed onto shore, or “wrack,” is an important component of shoreline ecosystems, providing habitat for macroinvertebrates and organic matter and nutrients to both the upland terrestrial communities and aquatic ecosystems. While marine wrack has been studied extensively, wrack along freshwater shorelines has received less attention. In this article, we report on the standing stocks, mobility, decomposition rates, and macroinvertebrate communities of wrack on different types of Hudson River shorelines (natural: sand, rock, bedrock; and engineered: riprap, cribbing, and bulkhead). Standing stocks of wrack sometimes exceeded 1 kg dry mass/m², and were the highest on shorelines having flat slopes. Artificial wrack (hay) placed below the high tide mark was rarely retained for more than a few tidal cycles, particularly on highly exposed shores. Wrack on cribbing shorelines decayed significantly faster than on other shoreline types. Macroinvertebrate abundance and diversity were significantly different among shoreline types, with the lowest abundance found on cribbing, along with significantly lower diversity. Consequently, if managers use structures such as cribbing and bulkheads to rebuild or reinforce shorelines, then certain ecological functions may be lost.     

Response of Heterotrophic Planktonic Bacteria to the Zebra Mussel Invasion of the Tidal Freshwater Hudson River

Abstract Invasions of aquatic ecosystems by exotic bivalves are known to cause dramatic changes in phytoplankton and some other groups, but their effect on the microbial component is unknown. The invasion of the tidal freshwater Hudson River by the exotic zebra mussel (Dreissena polymorpha) has caused large changes in several components of the Hudson's food web. Planktonic bacteria in the tidal freshwater Hudson are a major part of the food web, and mediate important processes in the carbon budget. We used a long-term data set, spanning four years prior to the zebra mussel (ZM) invasion and four years post-invasion, to describe ZM effects on planktonic bacteria. Small and meso-scale experiments were conducted to specifically examine direct consumption of bacteria by ZM, as well as effects on protozoans. Bacterial abundances in the Hudson have increased roughly 2× since the ZM arrived, making it clear that direct consumption by Dreissena is a minor process. Experiments show that ZM do not remove bacteria from Hudson River water, but are very effective at clearing flagellated protozoans, the major predator of bacteria. The observed changes in bacterial abundance have not been accompanied by equally large changes in bacterial productivity, suggesting growth is primarily limited by carbon supply. Bacterial production has not declined despite a dramatic decline of phytoplankton, confirming previous suggestions that bacteria and phytoplankton are not strongly linked in the Hudson. As a result of the increase in bacterial abundance and removal of phytoplankton, the absolute and relative contributions of bacterial carbon to living particulate organic carbon (POC) standing stocks have increased dramatically. The maintenance of the bacterial component of the Hudson River's food web may be one mechanism whereby consumers are ``insulated' from effects of zebra mussel consumption of phytoplankton carbon. Received: 24 October 1997; Accepted: 9 February 1998     

Effects of an invasive bivalve on the zooplankton community of the Hudson River

1. Previous studies documented that zebra mussels became abundant in the Hudson River during 1992 causing an 80–90% reduction in phytoplankton biomass. This study used intervention time series analysis of abundance, biomass and reproduction over the period 1987–95 to assess changes in zooplankton in response to the invasion.
2. Zebra mussels caused a size-dependent decline in zooplankton. Microzooplankton, including tintinnid ciliates, rotifers and copepod nauplii all declined in 1992 and were scarce thereafter. Mean abundances of post-naupliar copepods and of cladocerans were also lower following the invasion but these changes were not statistically significant ( P > 0.05). Egg ratios and clutch sizes for the dominant cladoceran, Bosmina freyi , were not significantly related to zebra mussels, even though relatively low egg ratios were observed after the invasion.
3. The strong declines in microzooplankton were probably caused by direct zebra mussel predation. Estimated consumption rates by mussels were roughly equivalent to maximum microzooplankton growth rates.
4. The total biomass of zooplankton in the Hudson River declined by more than 70% following the invasion. Annual average zooplankton biomass was correlated with chlorophyll, but biomass per unit chlorophyll in the Hudson River was much lower than in lakes. The present study hypothesizes that this lower biomass reflects limitations by riverine flow and by predation during summer.     

The Role of Surface and Subsurface Processes in Keeping Pace with Sea Level Rise in Intertidal Wetlands of Moreton Bay,Queensland, Australia

Increases in the elevation of the soil surfaces of mangroves and salt marshes are key to the maintenance of these habitats with accelerating sea level rise. Understanding the processes that give rise to increases in soil surface elevation provides science for management of landscapes for sustainable coastal wetlands. Here, we tested whether the soil surface elevation of mangroves and salt marshes in Moreton Bay is keeping up with local rates of sea level rise (2.358 mm y⁻¹) and whether accretion on the soil surface was the most important process for keeping up with sea level rise. We found variability in surface elevation gains, with sandy areas in the eastern bay having the highest surface elevation gains in both mangrove and salt marsh (5.9 and 1.9 mm y⁻¹) whereas in the muddier western bay rates of surface elevation gain were lower (1.4 and −0.3 mm y⁻¹ in mangrove and salt marsh, respectively). Both sides of the bay had similar rates of surface accretion (~7–9 mm y⁻¹ in the mangrove and 1–3 mm y⁻¹ in the salt marsh), but mangrove soils in the western bay were subsiding at a rate of approximately 8 mm y⁻¹, possibly due to compaction of organic sediments. Over the study surface elevation increments were sensitive to position in the intertidal zone (higher when lower in the intertidal) and also to variation in mean sea level (higher at high sea level). Although surface accretion was the most important process for keeping up with sea level rise in the eastern bay, subsidence largely negated gains made through surface accretion in the western bay indicating a high vulnerability to sea level rise in these forests.     

Original Articles: Sources of Dissolved Organic Carbon Supporting Planktonic Bacterial Production in the Tidal Freshwater Hudson River

Planktonic bacterial production in the tidal freshwater Hudson River is a major component of secondary productivity and is uncoupled from planktonic primary productivity. There are several major sources of allochthonous dissolved organic carbon (DOC) whose potential contribution to heterotrophic bacterial growth was examined with bioassays. Supply of DOC from the upper Hudson drainage basin and a large tributary in the mid-Hudson together comprise 70 kT DOC/year, which is the bulk of the DOC load to the tidal freshwater Hudson River. Two contrasting tidal wetlands contribute DOC to the main-stem river but were only a few percent of the tributary load even during summer low-flow conditions. The quantity of DOC released from fine sediments was intermediate to the other two loadings considered. Bacterial growth in bioassays receiving water from the sources varied, but differences in thymidine incorporation between reference and DOC sources were small, usually less than 2 nmol/L/h. Similarity in thymidine incorporation suggests that all sources of DOC were capable of supporting bacterial growth at approximately equal rates. Seasonal shifts in carbon availability were clear in several cases, for example, greater growth on wetland-derived DOC at times of peak plant productivity. Seasonal differences in tributary DOC bioavailability were not large despite the well-known seasonality of tributary inputs. Activities of a suite of extracellular enzymes were used as a biologically based characterization of DOC from the various sources. Shifts in allocation among enzymes were apparent, indicating that there are biologically relevant differences in composition among the sources. Fluorescence characteristics and absorbance per unit carbon also varied among sources, providing an independent confirmation of compositional differences among sources. The absence of large differences in bacterial productivity among sources suggests that growth is supported by a wide range of DOC, and the relative importance of the sources is probably related to the quantitative differences in inputs. Efforts to classify carbon supplies to ecosystems must recognize that organism plasticity in carbon use and physical mixing processes will both act to homogenize what might initially appear to be quite distinctive carbon inputs. Received 15 April 1997; accepted 17 February 1998     

Effects of Water Level on Three Wetlands Soil Seed Banks on the Tibetan Plateau

Background

Although the effect of water level on germination in soil seed banks has been documented in many ecosystems, the mechanism is not fully understood, and to date no empirical studies on this subject exist. Further, no work has been done on the effect of water level on seed banks of drying and saline-alkaline wetlands in alpine areas on the Tibetan Plateau.

Methodology

We examined the effects of water level (0 cm, 5 cm and 10 cm) on seed germination and seedling establishment from soil seed banks at 0–5 cm and 5–10 cm depths in typical, drying, and saline-alkaline wetlands. We also explore the potential role of soil seed bank in restoration of drying and saline-alkaline wetlands.

Principal Findings

Species richness decreased with increase in water level, but there almost no change in seed density. A huge difference exists in species composition of the seed bank among different water levels in all three wetlands, especially between 0 cm and 5 cm and 0 cm and 10 cm. Similarity of species composition between seed bank and plant community was higher in 0 cm water level in drying wetland than in the other two wetlands. The similarity was much higher in 0 cm water level than in 5 cm and 10 cm water levels in all three wetlands. Species composition of the alpine wetland plant community changed significantly after drying and salinization, however, species composition of the seed bank was unchanged regardless of the environment change.

Conclusions/Significance

Water level greatly affects seed bank recruitment and plant community establishment. Further, different water levels in restored habitats are likely to determine its species composition of the plant community. The seed bank is important in restoration of degraded wetlands. Successful restoration of drying and salinization wetlands could depend on the seed bank.     

Use of a Florida Gulf Coast Barrier Island by Spring Trans-Gulf Migrants and the Projected Effects of Sea Level Rise on Habitat Availability

Barrier islands on the north coast of the Gulf of Mexico are an internationally important coastal resource. Each spring hundreds of thousands of Nearctic-Neotropical songbirds crossing the Gulf of Mexico during spring migration use these islands because they provide the first landfall for individuals following a trans-Gulf migratory route. The effects of climate change, particularly sea level rise, may negatively impact habitat availability for migrants on barrier islands. Our objectives were (1) to confirm the use of St. George Island, Florida by trans-Gulf migrants and (2) to determine whether forested stopover habitat will be available for migrants on St. George Island following sea level rise. We used avian transect data, geographic information systems, remote sensing, and simulation modelling to investigate the potential effects of three different sea level rise scenarios (0.28 m, 0.82 m, and 2 m) on habitat availability for trans-Gulf migrants. We found considerable use of the island by spring trans-Gulf migrants. Migrants were most abundant in areas with low elevation, high canopy height, and high coverage of forests and scrub/shrub. A substantial percentage of forest (44%) will be lost by 2100 assuming moderate sea level rise (0.82 m). Thus, as sea level rise progresses, less forests will be available for migrants during stopover. Many migratory bird species’ populations are declining, and degradation of barrier island stopover habitat may further increase the cost of migration for many individuals. To preserve this coastal resource, conservation and wise management of migratory stopover areas, especially near ecological barriers like the Gulf of Mexico, will be essential as sea levels rise.     

Uncertainties in Measuring Populations Potentially Impacted by Sea Level Rise and Coastal Flooding

A better understanding of the impact of global climate change requires information on the locations and characteristics of populations affected. For instance, with global sea level predicted to rise and coastal flooding set to become more frequent and intense, high-resolution spatial population datasets are increasingly being used to estimate the size of vulnerable coastal populations. Many previous studies have undertaken this by quantifying the size of populations residing in low elevation coastal zones using one of two global spatial population datasets available – LandScan and the Global Rural Urban Mapping Project (GRUMP). This has been undertaken without consideration of the effects of this choice, which are a function of the quality of input datasets and differences in methods used to construct each spatial population dataset. Here we calculate estimated low elevation coastal zone resident population sizes from LandScan and GRUMP using previously adopted approaches, and quantify the absolute and relative differences achieved through switching datasets. Our findings suggest that the choice of one particular dataset over another can translate to a difference of more than 7.5 million vulnerable people for countries with extensive coastal populations, such as Indonesia and Japan. Our findings also show variations in estimates of proportions of national populations at risk range from <0.1% to 45% differences when switching between datasets, with large differences predominantly for countries where coarse and outdated input data were used in the construction of the spatial population datasets. The results highlight the need for the construction of spatial population datasets built on accurate, contemporary and detailed census data for use in climate change impact studies and the importance of acknowledging uncertainties inherent in existing spatial population datasets when estimating the demographic impacts of climate change.     

Impacts of Climate-Change-Driven Sea Level Rise on Intertidal Rocky Reef Habitats Will Be Variable and Site Specific

Intertidal rocky reefs are complex and rich ecosystems that are vulnerable to even the smallest fluctuations in sea level. We modelled habitat loss associated with sea level rise for intertidal rocky reefs using GIS, high-resolution digital imagery, and LIDAR technology at fine-scale resolution (0.1 m per pixel). We used projected sea levels of +0.3 m, +0.5 m and +1.0 m above current Mean Low Tide Level (0.4 m). Habitat loss and changes were analysed for each scenario for five headlands in the Solitary Islands Marine Park (SIMP), Australia. The results indicate that changes to habitat extent will be variable across different shores and will not necessarily result in net loss of area for some habitats. In addition, habitat modification will not follow a regular pattern over the projected sea levels. Two of the headlands included in the study currently have the maximum level of protection within the SIMP. However, these headlands are likely to lose much of the habitat known to support biodiverse assemblages and may not continue to be suitable sanctuaries into the future. The fine-scale approach taken in this study thus provides a protocol not only for modelling habitat modification but also for future proofing conservation measures under a scenario of changing sea levels.     

Rapid Communication: Climatic Control on Eutrophication of the Hudson River Estuary

Eutrophication is arguably the biggest pollution problem facing estuaries globally, with extensive consequences including anoxic and hypoxic waters, reduced fishery harvests, toxic algal blooms, and loss of biotic diversity. However, estuaries vary greatly in their susceptibility to eutrophication. The Hudson River estuary receives very high levels of nutrient inputs yet in the past has shown relatively low rates of phytoplankton productivity and is generally considered to be only moderately susceptible to eutrophication. Here, we show that eutrophication and primary production in the Hudson estuary can increase dramatically in response to climatic variation and lowered freshwater discharge from the watershed. During dry summer periods in 1995 and 1997, rates of primary production were substantially higher than those measured during the 1970s, when freshwater discharge tended to be high. In the Hudson, low freshwater discharge increases waterresidence times and stratification and deepens the photic zone, all of which (alone or in combination) could lead to the observed increase in primary production. Our data, along with the prediction of most climate change models that freshwater discharge will be lower in the future during the summer in the northeastern US, suggest that the Hudson will become more susceptible to eutrophication. Eutrophication in an estuary is a complex process, and climate change is likely to affect each estuary differently due to interactions with nutrient loadings and physical circulation. Hence, it is essential to consider the effects of climate change in the context of individual estuarine functioning to successfully manage eutrophication in the future. Received 22 December 1999; accepted 28 December 1999.     

Effects of the large-scale uncontrolled fertilisation process along the continental coastal North Sea

In this paper, effects of eutrophication in selected compartments of the North Sea ecosystem are discussed, encompassing the possibly positive effects of nutrient enrichment. Based on a variety of studies, impacts on biomass of phytoplankton, macrozoobenthos, microzooplankton, shrimps and fishes and productivity are presented. Enhanced nutrient concentrations and loadings can be observed in several coastal areas of the North Sea. As a result, increases in the concentration, production and changes in the species composition was observed in the phytoplankton. In addition, there are some indications for an increased biomass of macrozoobenthos, whereas an increase in microzooplankton can only be assumed from mesocosm experiments. A concomitant increase of higher trophic levels such as shrimps and fishes, as observed in some coastal regions of the North Sea, is difficult to link directly to eutrophication due to a lack of conclusive field observations showing the causality of the changes. That the large fertilisation process in the North Sea has led to a series of changes is, however, without doubt. The answer, to what extent these can be claimed as being harmless, positive or negative from the anthropogenic point of view, is hampered by the lack of good assessment criteria for marine ecosystems and requires a thorough analysis of all compartments involved by means of long-term-series long enough to discriminate between man-made and natural variability.     

Effects of water level on waterbird abundance and diversity along the middle section of the Danube River

We studied the effects of water level in the Danube River on waterbird species abundance and species assemblages along 83?km from the border of Hungary and Slovakia. 651,622 birds of 62 species were counted between 1992 and 2009. The dominant species was Mallard Anas platyrhynchos contributing 436,198 individuals (66.9% of all observations). Throughout the year total numbers of individuals and species richness were negatively correlated with local water level registered on the same day throughout the year. Shannon diversity indices were generally positively correlated with water levels. During floods, dabbling ducks, especially the dominant Anas platyrhynchos, dispersed to peripheral waters, where they are less likely to be counted, and diving ducks (Bucephala clangula, Aythya fuligula and Mergus spp.) left the area entirely, because fast flowing, highly turbid waters reduced local feeding efficiency. Abundance of most waterbird species decreased with elevated water levels. High water levels remove distinctive microhabitats (gravel banks, paved riverbanks and shoals), and create unfavourable conditions of high water velocity and turbidity. Retention of high water levels as a result of damming of the Danube creates long-term conditions similar to natural flooding effects. In our opinion, further manipulation of Danube water levels is likely to reduce waterbird richness and abundance and should be subject to appropriate environmental impact assessment.     

联户 牧民应对困境的自主选择 来自黄河首曲湿地的报道(二)

<正>我们的调查发现除了缺水之外,牧民们还遇到许多其它不曾遇到过的问题,这片土地承担着黄河生态安全的重责,却也同时经受着史无前例的变化和冲击,在政府实施各项举措的同时,牧民也在迷茫中用自己的方式寻找着出路。     

Tidal impact on planktonic primary and bacterial production in the German Wadden Sea

 Tidal variation of biological parameters was studied at three anchor stations in selected inlet channels of the northern German Wadden Sea in May and July 1994. Concentrations of bacteria, chlorophyll a and suspended matter as well as primary and bacterial production were assessed over a period of 25 h in the surface and in the bottom water. Diurnal variation in primary production was found both under in situ light conditions and under constant illumination. Tidal turbulence caused the introduction of detritus, bacteria and pigments from the sediment into the water column. The impact of sediment resuspension was most evident in the bottom water, leading to tidally oscillating bacterial production rates which were high during high stream velocity and low during the slack times. Estimations of the areal daily phytoplankton production and corresponding bacterial carbon demands were unbalanced. Primary production accounted for only 25–45% of the total bacterial carbon requirement. This discrepancy is due to the shallow euphotic depth in the Wadden Sea, allowing net primary production only in the upper 2–3 m of the water column, while the relatively high levels of bacterial activity do not show a vertical decline. Assuming that the specific biological activities in the water columns over the tidal flats are similar to those found in the inlet channels, it was found that production processes dominate in shallow areas whereas decomposition processes dominate in the deep channels. Moreover, the predominance of heterotrophic processes in the inlet channels means that additional organic carbon sources must contribute to the heterotrophic metabolism in the deep parts of the Wadden Sea, and that the horizontal flux of material is important in this turbid mesotidal ecosystem. Received: 18 April 1998 / Accepted: 12 November 1998     

Biotic disturbance in expanding subarctic forests along the eastern coast of Hudson Bay

* The past and present occurrence of insect disturbance on white spruce (Picea glauca) trees was evaluated at their northern range limit on the eastern coast of Hudson Bay, and its effects on tree growth and population dynamics studied. * Three sites were sampled along an altitudinal gradient. Ring-width chronologies and stem analysis were used to evaluate tree growth. The occurrence of holes in the bark, of resin pockets and blue-stain fungi, and ring-width evidence for growth releases were used to assess the impact of bark beetle. * The white spruce population was established at these sites in the 17th century. Since their establishment, the spruce trees have developed a tree growth form, except at the uppermost site, where severe growth suppression occurred in the 19th century. Bark beetle and blue-stain fungi occurred with different timing and intensity. Their highest occurrence, associated with high mortality rates, was at the lowest site in the late 20th century. In the uppermost sites, biotic disturbance has occurred since the 18th century, associated with evidence for mechanical disturbance. * The simultaneous arrival of white spruce in the area resulted in a synchronous onset of spruce beetle activity driven by tree ageing. Unfavourable climatic conditions affected tree growth severely in the most exposed sites.     

Site History and Edaphic Features Override the Influence of Plant Species on Microbial Communities in Restored Tidal Freshwater Wetlands

Restored wetland soils differ significantly in physical and chemical properties from their natural counterparts even when plant community compositions are similar, but effects of restoration on microbial community composition and function are not well understood. Here, we investigate plant-microbe relationships in restored and natural tidal freshwater wetlands from two subestuaries of the Chesapeake Bay. Soil samples were collected from the root zone of Typha latifolia, Phragmites australis, Peltandra virginica, and Lythrum salicaria. Soil microbial composition was assessed using 454 pyrosequencing, and genes representing bacteria, archaea, denitrification, methanogenesis, and methane oxidation were quantified. Our analysis revealed variation in some functional gene copy numbers between plant species within sites, but intersite comparisons did not reveal consistent plant-microbe trends. We observed more microbial variations between plant species in natural wetlands, where plants have been established for a long period of time. In the largest natural wetland site, sequences putatively matching methanogens accounted for ∼17% of all sequences, and the same wetland had the highest numbers of genes coding for methane coenzyme A reductase (mcrA). Sequences putatively matching aerobic methanotrophic bacteria and anaerobic methane-oxidizing archaea (ANME) were detected in all sites, suggesting that both aerobic and anaerobic methane oxidation are possible in these systems. Our data suggest that site history and edaphic features override the influence of plant species on microbial communities in restored wetlands.     

Threatened and Endangered Subspecies with Vulnerable Ecological Traits Also Have High Susceptibility to Sea Level Rise and Habitat Fragmentation

The presence of multiple interacting threats to biodiversity and the increasing rate of species extinction make it critical to prioritize management efforts on species and communities that maximize conservation success. We implemented a multi-step approach that coupled vulnerability assessments evaluating threats to Florida taxa such as climate change, sea-level rise, and habitat fragmentation with in-depth literature surveys of taxon-specific ecological traits. The vulnerability, adaptive capacity, and ecological traits of 12 threatened and endangered subspecies were compared to non-listed subspecies of the same parent species. Overall, the threatened and endangered subspecies showed high vulnerability and low adaptive capacity, in particular to sea level rise and habitat fragmentation. They also exhibited larger home ranges and greater dispersal limitation compared to non-endangered subspecies, which may inhibit their ability to track changing climate in fragmented landscapes. There was evidence for lower reproductive capacity in some of the threatened or endangered taxa, but not for most. Taxa located in the Florida Keys or in other low coastal areas were most vulnerable to sea level rise, and also showed low levels of adaptive capacity, indicating they may have a lower probability of conservation success. Our analysis of at-risk subspecies and closely related non-endangered subspecies demonstrates that ecological traits help to explain observed differences in vulnerability and adaptive capacity. This study points to the importance of assessing the relative contributions of multiple threats and evaluating conservation value at the species (or subspecies) level when resources are limited and several factors affect conservation success.