Cordgrass Spartina Alterniflora Research Articles

A fiddler crab reduces plant growth in its expanded range.

Species across the planet are shifting or expanding their ranges because of climate change. These are climate migrants. Although climate migrants are well documented, their impacts on recipient ecosystems are not. Climate migrants that are also ecosystem engineers (species that modify or create habitats) will likely have profound effects on ecosystems. The Atlantic marsh fiddler crab, Minuca pugnax, is a burrowing crab that recently expanded its range into the northeastern United States. In its historical range, M. pugnax enhances the aboveground growth of the cordgrass Spartina alterniflora, a plant critical to marsh persistence. In a control-impact study, however, we found that Spartina aboveground biomass was 40% lower when M. pugnax was present. Thus, the positive effect of M. pugnax on Spartina aboveground biomass flipped to a negative one in its expanded range. Spartina belowground biomass was also 30% lower on average when crabs were present, a finding consistent with what is seen in the historical range. These impacts on Spartina are likely due to burrowing by M. pugnax. Benthic microalgae was, on average, 45% lower when crabs were present. Fiddler crabs eat benthic microalgae, and these results suggest that fiddler crabs can control algal biomass via grazing. Because fiddler crabs reduced the biomass of foundational primary producers in its expanded range, our results imply that M. pugnax can influence other saltmarsh functions such as carbon storage and accretion as they expand north. Most strikingly, our results suggest that as species expand or shift their range with climate change, not only can they have profound impacts in their new ranges but those impacts can be the inverse of what is seen in their historical ranges.

The native reed-specific bird, reed parrotbill, has been detected in exotic smooth cordgrass.

After the smooth cordgrass Spartina alterniflora invaded coastal China, native birds started avoiding the green desert, and bird diversity declined. After many years, a few passerine birds began to enter and use smooth cordgrass, but only birds with a nonspecialised habitat. In this study, we found that a native reed-specific bird, the parrotbill Calamornis heudei, flocked and sang in a smooth cordgrass habitat throughout the overwintering period near Sheyang Port in Yancheng, Jiangsu Province. This observation suggests that native obligate birds may be forced to adapt to exotic smooth cordgrass habitats after long-term coexistence, which would, obviously, affect the distribution, feeding and reproduction of birds. The concern is that this could be an ecological trap, leading to unknown consequences. More research is required to examine the process occurring along the Chinese coast.

Cordgrass Spartina alterniflora acts as a key carbon source to support macrozoobenthos in the salt marsh and nearby mudflat communities

Exotic cordgrass Spartina can influence the trophic interaction and functioning of coastal ecosystems by altering the availability or palatability of carbon sources utilized by macrozoobenthos. Previous studies focused mainly on the trophic dynamics in Spartina-invaded mangroves or marshes, but the effect of Spartina on the diet of macrozoobenthos inhabiting the nearby unvegetated mudflat remains largely unexplored. By analyzing carbon and nitrogen stable isotopes, we compare the trophic contribution of an exotic cordgrass Spartina alterniflora to the macrozoobenthos between the dense S. alterniflora area (DSA) and adjacent tidal bare mudflat (TBM) in the Hepu coast, Guangxi province. Macrozoobenthic species were more abundant in TBM than in DSA, but the difference in carbon and nitrogen stable isotopes was insignificant for the seven conspecifics between two sampling areas, where similar organic carbon sources and trophic levels for macrozoobenthos were found. The MixSIAR mixing model revealed that S. alterniflora acted as the most important carbon source for many macrozoobenthic species and all guilds in DSA and TBM. This study showed that S. alterniflora can benefit the adjacent bare mudflat by supplying detritus as the carbon source for macrozoobenthos, which is favorable for maintaining the biodiversity and trophic dynamics of macrozoobenthic communities in coastal ecosystems.

Chemically mediated rheotaxis of endangered tri-spine horseshoe crab: potential dispersing mechanism to vegetated nursery habitats along the coast.

An enhanced understanding of larval ecology is fundamental to improve the management of locally depleted horseshoe crab populations in Asia. Recent studies in the northern Beibu Gulf, China demonstrated that nesting sites of Asian horseshoe crabs are typically close to their nursery beaches with high-density juveniles distributed around mangrove, seagrass and other structured habitats. A laboratory Y-maze chamber was used to test whether the dispersal of early-stage juvenile tri-spine horseshoe crab Tachypleus tridentatus is facilitated by chemical cues to approach suitable nursery habitats. The juvenile orientation to either side of the chamber containing controlled seawater or another with various vegetation cues, as well as their movement time, the largest distance and displacement were recorded. The juveniles preferred to orient toward seagrass Halophila beccarii cues when the concentration reached 0.5 g l-1, but ceased at 2 g l-1. The results can be interpreted as a shelter-seeking process to get closer to the preferred settlement habitats. However, the juveniles exhibited avoidance behaviors in the presence of mangrove Avicennia marina and invasive saltmarsh cordgrass Spartina alterniflora at 2 g l-1. The juveniles also spent less time moving in the presence of the A. marina cue, as well as reduced displacement in water containing the S. alterniflora cue at 1 and 2 g l-1. These results may explain the absence of juvenile T. tridentatus within densely vegetated areas, which have generally higher organic matter and hydrogen sulfide. Early-stage juvenile T. tridentatus are capable of detecting and responding to habitat chemical cues, which can help guide them to high-quality settlement habitats. Preserving and restoring seagrass beds in the intertidal areas should be prioritized when formulating habitat conservation and management initiatives for the declining horseshoe crab populations.

The Opposite of Biotic Resistance: Herbivory and Competition Suppress Regeneration of Native but Not Introduced Mangroves in Southern China

Mangrove forests are increasingly threatened by plant invasions worldwide, but some mangrove species are invasive and threaten salt marsh and native mangrove ecosystems. The southern coast of China is invaded by the cordgrass Spartina alterniflora, and the mangrove Sonneratia apetala, providing a model system for studying the processes and mechanisms through which non-native species establish and spread. We used a transplant experiment to test the overarching hypothesis that native herbivores and plants provided biotic resistance against invasion by S. apetala, and that the importance of these factors would vary geographically. Survival of transplanted mangrove seedlings was lower in Zhangjiang Estuary (23°55′ N) than in Leizhou Bay (20°56′ N), and varied with species and habitats. S. apetala had higher survival and growth rates than native mangroves at both sites, and S. apetala grew taller than the S. alterniflora canopy at Leizhou Bay in only two growing seasons. In contrast, native mangroves grew poorly in S. alterniflora. Grazing by rodents and insects suppressed the growth and survival of Kandelia obovata and Avicennia marina in Zhangjiang Estuary and Leizhou Bay, but had little effect on S. apetala. Competition with vegetation (S. alterniflora and native mangroves) exacerbated the reduced survival of native mangroves, and these effects varied across study sites. Low survival of non-native S. apetala in vegetated habitats at Zhangjiang Estuary was likely due to a synergistic effect of low winter temperatures and low light intensity. Escape from herbivory (the opposite to biotic resistance) and fast growth may drive the quick expansion of non-native S. apetala in China. Rapid encroachment of S. apetala may transform the native mangrove forests and monospecific intertidal Spartina grasslands into non-native mangrove forests in the southern coast of China.

Effects of Smooth Cordgrass Spartina alterniflora Invasion on Macrobenthic Fauna in the Yellow River Delta

Effects of Smooth Cordgrass Spartina alterniflora Invasion on Macrobenthic Fauna in the Yellow River Delta

Pareuzebyella sediminis gen. nov., sp. nov., a novel marine bacterium in the family Flavobacteriaceae, isolated from a tidal flat sediment.

Two marine bacterial strains, designated S2-4-21T and MT2-5-19, were isolated from two tidal flat sediments of cordgrass Spartina alterniflora and adjacent oyster culture field in Quanzhou bay, China, respectively. Both strains were Gram-staining-negative, rod-shaped, non-flagellated, non-motile, aerobic, had NaCl requirements, and contained carotenoid and flexirubin pigments. The 16S rRNA gene sequence similarity (99.8%), average nucleotide identity value (99.4%) and average amino acid identity (99.3%) between strain S2-4-21T and strain MT2-5-19 strongly supported that they belonged to a single species. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S2-4-21T and strain MT2-5-19 formed a monophyletic branch affiliated to the family Flavobacteriaceae, sharing similarities of 94.6% with Euzebyella marina CY01T and E. saccharophila 7SM30T, and of 94.1 and 92.8% with E. algicola MEBiC 12267T and Pseudozobellia thermophile DSM 19858T, respectively. Phylogenomic analysis based on the whole genome sequences supported that the two strains formed a distinct monophyletic clade within Flavobacteriaceae members, which was phylogenetically different from the clades of Euzebyella and Pseudozobellia. The major respiratory quinone was menaquinone MK-6. The major fatty acids (>10%) consisted of C15 : 0 iso, C16 : 0, summed feature 9 (C17 : 1 iso ω9c/C16 : 0 10-methyl) and C17 : 0 iso 3-OH. The polar lipid profiles of strain S2-4-21T and strain MT2-5-19 are identical, including phosphatidylethanolamine, four unidentified aminolipids, and four unidentified lipids. The genomic size was 4.9-5.0 Mb with genomic DNA G+C content of 41.5 mol%. Based on the above characteristics, strains S2-4-21T and MT2-5-19 represented a novel species of a novel genus in the family Flavobacteriaceae. Thus, Pareuzebyella sediminis gen. nov. sp. nov. is proposed with type strain S2-4-21T (=MCCC 1K03818T=KCTC 72152T), and another strain MT2-5-19 (=KCTC 72539=MCCC 1K03874).

Predators enhance resilience of a saltmarsh foundation species to drought

Abstract Disturbances are increasing in size and frequency with climate change, facilitating species that opportunistically exploit areas where habitat‐forming foundation species have been removed. Although it is well‐recognized that consumers, disease and weedy space‐holders can affect foundation species’ resistance to and recovery from disturbance, how predators influence their resilience is less clear. In salt marshareas de‐vegetated by drought and intensive snail Littoraria irrorata grazing (hereafter, ‘die‐offs’), we monitored bird use and experimentally manipulated bird and nekton access to the vegetated borders of die‐off mudflats across periods of both vegetation die‐off and regrowth to explore how these predators mediate the resilience of cordgrass Spartina alterniflora, the foundation species that structures US Atlantic coast salt marshes. Surveys revealed that birds, especially probers that agitate soils, forage year‐round for invertebrates in die‐off mudflats in our study area but not in adjacent vegetated areas. During periods of die‐off, cordgrass borders accessible to bird and nekton predators retreated >3‐times slower and snail densities were halved, relative to predator exclusion cages. In predator‐accessible plots, slower border retreat corresponded to greater snail infection by a bird host‐dependent trematode parasite. During recovery, cordgrass borders revegetated more quickly, and snail densities declined faster over time in unmanipulated controls relative to predator exclusions. Synthesis. These findings suggest that birds, through their transmission of parasites to snails, appear to act synergistically with snail‐consuming nekton to slow cordgrass loss after drought‐snail disturbances. Predator access also corresponds to faster cordgrass recovery as environmental conditions improve, although the mechanisms behind this need further investigation. Thus, predators that opportunistically forage within disturbances have the potential to suppress consumer impacts through multiple mechanisms, including consumption and disease transmission, thereby bolstering foundation species’ resilience and modulating whole ecosystem responses to climate change.

Spartinivicinus ruber gen. nov., sp. nov., a Novel Marine Gammaproteobacterium Producing Heptylprodigiosin and Cycloheptylprodigiosin as Major Red Pigments.

The red pigment prodiginines are identified as bacterial secondary metabolites and display a wide range of bioactive properties. Here, a novel rose-red pigmented bacterium, designated strain S2-4-1HT, was isolated from coastal sediment of cordgrass Spartina alterniflora. Interestingly, it simultaneously produced heptylprodigiosin (C22H29N3O) and cycloheptylprodigiosin (C22H27N3O) as major red pigments, of which their chemical structures were established by liquid chromatography–mass spectrometry (LC–MS) and nuclear magnetic resonance (NMR). Bioactive assays revealed that both heptylprodigiosin and cycloheptylprodigiosin had antibacterial and antifungal activities, and notably, cycloheptylprodigiosin showed stronger bioactivity than heptylprodigiosin. The complete genome of strain S2-4-1HT was determined to be 6,687,090 bp in length with a G + C content of 40.13 mol%, including a circular chromosome with a size of 6,361,125 bp and three plasmids with a size of 141,078, 102,423, and 82,464 bp, respectively. The biosynthetic gene cluster of two red pigments was predicted on a ∼41-kb gene fragment organized on the chromosome and displayed highly conserved features compared to several gammaproteobacterial species encoding the homologous genes. Finally, based on phenotypic, genotypic, and chemotaxonomic characteristics, strain S2-4-1HT represented a novel genus-level species named Spartinivicinus ruber gen. nov., sp. nov. (type strain S2-4-1HT = MCCC 1K03745T = KCTC 72148T). Our study provided a novel bacterial source and novel prodigiosin analogs as promising pharmaceuticals in biotechnological application.

Negative indirect effects of hurricanes on recruitment of range-expanding mangroves

Disturbances often have positive, direct effects on invasions by dispersing propagules or creating environmental conditions that favor invasive species. However, disturbances that alter interactions between resident and invading species could also affect invasion success. In northeast Florida, the black mangrove Avicennia germinans is expanding into salt marshes, where it interacts with the dead litter (wrack) of the native marsh cordgrass Spartina alterniflora. From 2015-2017, we performed monthly surveys before and after 2 hurricanes in 3 marsh microhabitats (bare sediment, vegetation, wrack) to quantify mangrove propagule and seedling densities. Wrack increased propagule retention up to 10 times relative to other microhabitats. Hurricanes did not directly harm mangrove propagules or seedlings. However, storm surge relocated wrack to upland environments, which indirectly inhibited mangroves by temporarily disrupting the facilitative effects of wrack on propagule recruitment and exposing intertidal bare patches that decreased propagule retention and seedling establishment. Wrack remained absent from intertidal areas for 1-3 mo. Because hurricane season overlaps with propagule recruitment, hurricane timing and wrack return time to intertidal areas influence the degree that hurricanes disrupt wrack-mangrove interactions. We demonstrate that large-scale disturbances can negatively and indirectly affect invader recruitment by altering interactions with resident species.

Submergence, nutrient enrichment, and tropical storm impacts on Spartina alterniflora in the microtidal northern Gulf of Mexico

Salt marshes face chronic anthropogenic impacts such as relative sea level rise and eutrophication, as well as acute disturbances from tropical storms that can affect the productivity of these important communities. However, it is not well understood how marshes already subjected to eutrophication and sea level rise will respond to added effects of episodic storms such as hurricanes. We examined the interactive effects of nutrient addition, sea level rise, and a hurricane on the growth, biomass accumulation, and resilience of the saltmarsh cordgrass Spartina alterniflora in the Gulf of Mexico. In a microtidal marsh, we manipulated nutrient levels and submergence using marsh organs in which cordgrasses were planted at differing intertidal elevations and measured the impacts of Hurricane Isaac, which occurred during the experiment. Prior to the hurricane, grasses at intermediate and high elevations increased in abundance. After the hurricane, all treatments lost approximately 50% of their shoots, demonstrating that added nutrients and elevation did not provide resistance to hurricane disturbance. At the end of the experiment, only the highest elevations had been resilient to the hurricane, with increased above- and belowground growth. Added nutrients provided a modest increase in above- and belowground growth, but only at the highest elevations, suggesting that only elevation will enhance resilience to hurricane disturbance. These results empirically demonstrate that S. alterniflora in microtidal locations already subjected to submergence stress is less able to recover from storm disturbance and suggests we may be underestimating the loss of northern Gulf Coast marshes due to relative sea level rise.

Ribbed mussel (Geukensia demissa) filtration services are driven by seasonal temperature and site-specific seston variability

Ribbed mussels (Geukensia demissa) are ubiquitous intertidal invertebrates of eastern North American salt marshes, often living in close association with salt marsh cordgrass Spartina alterniflora. They are typically concentrated at the lower extent of the vegetated zone along tidal channels, but are also found across the marsh platform. As filter-feeding bivalves, ribbed mussels remove suspended micro-particulate matter and associated nutrients from the water column, potentially resulting in benefits to water quality. However, the magnitude of such ecosystem services may depend on temporal and spatial variation in the mussel's water clearance and particle filtration rates. The goal of this study was to identify sources of variation regarding the distribution of ribbed mussel filtration services.Seasonal-spring, summer, and fall- water clearance and particle filtration rates were quantified for ribbed mussels collected from three habitats- low marsh along main tidal channels; low marsh along intra-marsh creek networks; and from the high marsh- and replicated in four representative marshes- three in New Jersey and one in Rhode Island, USA, normalized by mussel dry tissue biomass. Clearance rates varied with seasonal temperatures, but exhibited low spatial variability among habitats and marshes, highlighting the importance of understanding the temporal physiological variability when calculating annual rates. In contrast, filtration rates were highly variable, driven largely by spatial variation in seston availability. Annual bulk filtration services provided by ribbed mussels are therefore largely driven by both temporal variability in water processing and spatial variations in food availability, and can therefore be predicted by integrating seasonal clearance rates and site-specific seston composition.

Detrital traits affect substitutability of a range‐expanding foundation species across latitude

Climate‐driven range shifts of foundation species could alter ecosystem processes and community composition by providing different resources than resident foundation species. Along the US Atlantic coast, the northward expanding foundation species, black mangrove Avicennia germinans, is replacing the dominant salt marsh foundation species, marsh cordgrass Spartina alterniflora. These species have distinct detrital attributes that ostensibly provide different resources to epifauna. We experimentally examined how detritus of these species affects decomposition and community composition in different habitat contexts at regional and local scales. First, we manipulated detritus identity (Avicennia, Spartina) at 13 sites across a 5° latitudinal gradient spanning mangrove, mixed marsh‐mangrove and salt marsh habitats. Across latitude, we found that Avicennia detritus decomposed 2–4 times faster than Spartina detritus, suggesting that detrital turnover will increase with mangrove expansion. Epifaunal abundance and richness increased 2–7 times from south to north (mangrove to salt marsh) and were equivalent between Avicennia and Spartina detritus except for crabs, a dominant taxonomic group that preferred Spartina detritus. Second, to examine the whether changing habitat context affected regional patterns, we manipulated detritus identity and surrounding habitat type (mangrove, salt marsh) at a single mixed site, also including inert mimics to separate structural and nutritional roles of detritus. Epifaunal richness was similar between the two detrital types, but crabs were 2–7 times more abundant in Spartina detritus due to its structural attributes. Surrounding habitat type did not influence decomposition rate or community patterns, which suggests that latitudinal influences, not surrounding habitat, drove the regional community patterns in the first experiment. Overall, mangrove expansion could alter epifaunal communities due to the lower structural value and faster turnover of mangrove detritus. As species shift with changing climate, understanding foundation species substitutability is critical to predict community change, but we must account for concomitant environmental changes that also modify communities.

Burrowing Crabs Weaken Mutualism Between Foundation Species

Foundation species often interact with each other and co-create habitat upon which other species depend. Whether the presence of these facilitated species feeds back to mediate the growth and resilience of the foundation species themselves, and influence the strength of their interactions, remains poorly understood. In a 16-month field experiment in a southeastern US salt marsh, we tested how the overlapping presence of two foundation species, cordgrass (Spartina alterniflora) and ribbed mussels (Geukensia demissa), influences the abundance of facilitated species, specifically burrowing crabs (mainly Uca pugnax), and how crabs, in turn, affect each foundation species and their mutualistic interaction. Mussel aggregations enhanced crab abundance 3.9-fold, which in turn reduced both mussel and cordgrass growth and stifled cordgrass recovery after a simulated disturbance. Porewater and plant tissue analyses suggest crabs reduced cordgrass growth by reducing nitrogen availability, damaging roots, and potentially interfering with mussel deposition of nutrient-rich pseudofeces. A five-site field survey along 700 km southeastern US coastline revealed that cordgrass biomass and crab abundance are consistently higher in mussel aggregations. Furthermore, cordgrass biomass correlated negatively with crab abundance, supporting our experimental findings and the hypothesis that facilitated biota can negatively impact the foundation species upon which they depend. We anticipate that such negative, but non-lethal, feedbacks between foundation species and the biota they facilitate may be a common but overlooked phenomenon controlling foundation species growth and interactions in a wide range of ecosystems.

Effect of exotic cordgrass Spartina alterniflora on the eco-exergy based thermodynamic health of the macrobenthic faunal community in mangrove wetlands

The health of natural ecosystems, including mangrove wetlands, is being severely challenged by biological invasions worldwide. For a holistic evaluation of ecosystem health, researchers have commonly measured the eco-exergy of the system in question. Mangrove wetlands depend on their macrobenthic fauna and are threatened by the exotic cordgrass Spartina alterniflora, particularly in South China. However, the effect of S. alterniflora on the health status of macrobenthic faunal community in such wetlands is still unclear. In this study in Zhanjiang, China, eco-exergy was measured to compare the health status of macrobenthic faunal communities in (1) an Avicennia marina monoculture vs. an S. alterniflora-invaded A. marina stand (an A. marina and S. alterniflora mixture) and in (2) an unvegetated shoal vs. an S. alterniflora-invaded shoal that had rapidly become an S. alterniflora monoculture. Macrobenthic faunal community eco-exergy and biomass but not specific eco-exergy were lower in S. alterniflora-invaded mangrove habitats than in non-invaded ones. In terms of eco-exergy, mollusks were the dominant group in all habitats, and were mainly responsible for the decrease in eco-exergy in the invaded habitats. Differences in the eco-exergy of the macrobenthic faunal community in S. alterniflora-invaded habitats were mainly associated with differences in sediment physicochemical properties and vegetation characteristics in general and with the greater plant density in invaded habitats in particular. The results indicate that the health of the macrobenthic faunal community in mangrove wetlands has been reduced by S. alterniflora invasion and the conservation of ecosystem health in mangrove wetlands will require eradication of S. alterniflora.

Influence of two non-indigenous plants on intertidal macrobenthic communities in Ximen Island Special Marine Protected Area, China

Many coastal habitats are being substantially altered by non-indigenous plants (NIP). In the present study, intertidal macrobenthic communities of three habitats – a non-vegetated tidal flat (TF), a marsh with the smooth cordgrass Spartina alterniflora (SA) and a Kandelia candel mangrove forest (KC) – were examined during periods of ebb tide in February, May, August and November 2015 in Ximen Island Special Marine Protected Area, Zhejiang Province, China. S. alterniflora was introduced from North America in 1979 and invaded Ximen Island spontaneously. K. candel was a direct, artificial introduction in 1957 from Fujian, China. A total of 48 species of macrobenthos were collected from Ximen Island. The average density of macrobenthos in TF, SA and KC was 1365, 1398 and 669 ind./m2, respectively, and the average biomass of macrobenthos in TF, SA and KC was 144.13, 43.00 and 138.70 g/m2, respectively. There were no significant differences among the three habitats on density and biomass of macrobenthos, with the exception of density in spring and biomass in autumn. Diversity indices of macrobenthos did not exhibit significant differences among the three habitats, except for Margalef’s richness index (d) in KC. However, Results of one-way analysis of similarity (ANOSIM) revealed significant differences in macrobenthic community structure among the three habitats and four seasons. It was concluded that, although few significant differences were observed in the density, biomass and diversity indices of macrobenthos among habitats, there were significant changes in the macrobenthic communities’ structure after the introduction of S. alterniflora and K. candel. Therefore, when we use plants as ecological engineering materials, we need to take into account all of their potential ecological consequences.

Effects of short-term invasion of Spartina alterniflora and the subsequent restoration of native mangroves on the soil organic carbon, nitrogen and phosphorus stock

The exotic cordgrass Spartina alterniflora has severely invaded the mangrove wetlands in southern China and ecological restoration using native mangroves was conducted in an attempt to control this invasive species. In this study, the contents and pools of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) were quantified to investigate the invasive effects of S. alterniflora and then to evaluate whether the ecological restoration of native mangrove could reverse those effects. S. alterniflora only showed significantly higher organic carbon content in the surface 0–10 cm of soil than in the uninvaded mudflat. The high δ13C values in the surface soil of the invaded habitat demonstrated that S. alterniflora contributed 42.6–62.2% of the organic carbon. The SOC for invasive S. alterniflora and newly restored mangroves (4 years and 14 years) was not enhanced in comparison to the unvegetated mudflat. S. alterniflora significantly increased the surface soil TN content, but decreased the available phosphorus content and TP density. The TN densities increased gradually with the mangrove restoration, while the TP densities were only slightly influenced. The results suggested that short-term invasion of S. alterniflora and subsequent mangrove restoration did not alter SOC or TN pool sizes, but S. alterniflora was shown to affect the potential carbon storage capacity produced by the mangroves in the Zhangjiang Estuary.

Leveraging limited information to understand ecological relationships of endangered Florida salt marsh vole

Abstract We were able to substantially increase our knowledge of what is likely the least understood endangered terrestrial mammal in the United States, the Florida salt marsh vole (FSMV; Microtus pennsylvanicus dukecampbelli). We developed a predictive landscape model that estimated 264 ha of potential habitat for FSMVs. Evaluating our model, we found voles at 8 of the 36 sites sampled, yielding a model accuracy of 22% for a subspecies that previously was known from only 3 locations. Within areas of potential habitat, FSMVs selected patches of marsh vegetation > 0.49 ha with at least some (≥ 16.75% and ≤ 43.61%) smooth cordgrass (Spartina alterniflora) cover. Suggestive of a meta-population dynamic, FSMV activity decreased outside of patches of smooth cordgrass and saltgrass (Distichlis spicata) identified by the predictive landscape model. Our hierarchical approach to studying FSMVs allowed us to leverage a limited amount of data to ultimately produce important ecological information about an endangered species. This approach easily may be adapted to other mammals with similar information needs.

Utilization of exotic Spartina alterniflora by fish community in the mangrove ecosystem of Zhangjiang Estuary: evidence from stable isotope analyses

The cordgrass Spartina alterniflora has invaded mangrove-dominated habitats in China during the last few decades. However, the ecological effect of the S. alterniflora on the mangrove fish community is poorly understood. In order to assess the relative nutritional contributions of native autotrophs (benthic microalgae: BMA, particulate organic matter: POM, C3 native mangrove Aegiceras corniculatum, Avicennia marina and Kandelia obovata) and C4 exotic S. alterniflora, we examined the stable carbon and nitrogen isotope values of six common fish species (Osteomugil ophuyseni, Coilia grayii, Parachaeturichthys polynern, Sparus latus, Lateolabrax japonicas and Ophichthus apicalis) in the tidal creek of Zhangjiang Estuary. Results of the MixSIR model suggested that exotic S. alterniflora combined with BMA constituted major food sources of the fish community. S. alterniflora had a higher median contribution than all the other food sources to all fish species except for P. polynerna and S. latus, which derived their major food sources from BMA. These results indicated that the invasive cordgrass has been incorporated into the local aquatic food web through providing important nutrient source for fish species in the mangrove ecosystem of Zhangjiang Estuary.

A new non-indigenous Crassostrea species in Southwest Atlantic salt marshes affects mortality of the cordgrass Spartina alterniflora

Biological invasions in marine and coastal systems may produce new trophic and nontrophic interactions influencing the structure of the invaded community. In the intertidal salt marshes of Samborombón Bay (36°19′20″S, 56°46′26″W; mouth of La Plata River; Argentina), there is a new non-indigenous oyster species, Crassostrea sp., which settles on the dominant smooth cordgrass Spartina alterniflora. Here, we analyzed if the oyster affects S. alterniflora. Sampling showed that density of live plant was similar across intertidal levels, but there were higher density of dead plant stems at low intertidal levels. This pattern coincides with higher density and larger shell size of Crassostrea sp. at the low intertidal where oysters are attached to the basal part of the plant stems. An experiment manipulating oysters attached to S. alterniflora stems and oyster mimics shows that Crassostrea sp. can indeed increase mortality of S. alterniflora. The negative effect of bivalves on plant could be because several oysters settle around the Spartina stem, and by growing during the year, strangle the plants increasing their mortality rate. Together, all these evidences strongly suggest that these non-indigenous oysters can control the lower intertidal level of plant distribution in this system.