Faunal Density Research Articles

Climate change enhances soil fauna population and biomass in grasslands of the Loess Plateau

Soil fauna is a crucial component of soil biodiversity, which affects various processes and functions in terrestrial ecosystems. However, few quantitative, large-scale spatially distributional studies have explored the abundance and biomass of soil fauna. In this study, the 95 areas at 19 sites in the Loess Plateau region were surveyed. Numerous individual samples of soil fauna and environmental factors such as climate, soil and vegetation on which soil fauna depended were collected and identified. The results indicate that the soil fauna of the Loess Plateau grassland can be classified into 3 phyla, 10 classes and 23 orders, with an average soil fauna density of about 2 × 104 ind. m−2, and an average biomass of about 18 g m−2. Notably, the soil fauna density and biomass decreased significantly as the latitude increased, and the overall spatial distribution pattern revealed a gradual decrease from southeast to northwest in the Loess Plateau. We found that climatic factors, especially precipitation, primarily drove the spatial distribution of soil fauna density and biomass, contributing 72% and 58%, respectively. Conservatively estimated, the number of soil fauna on the Loess Plateau exceeds 4 × 1015, with the estimated total biomass of 4 × 106 t, equivalent to 2 Mt carbon. In addition, model predictions indicate that soil fauna populations and biomass of grassland in the Loess Plateau increased 27% and 29%, from 2000 to 2022. This study highlights major ecological and geographical gaps in the current knowledge of soil fauna, provides ideas for enhancing the accuracy of global soil fauna biomass assessments, and presents new perspectives to guide further investigations into the precise contribution of soil fauna to the soil carbon cycling.

Long-term monitoring of macroinvertebrate dynamics in response to climate and hydropower drivers in a glacier-fed Alpine stream

Alpine riverine ecosystems are highly sensitive to climate change and anthropogenic pressures, yet they provide critical ecosystem services, including downstream water resources. Glacier-fed streams, such as the Saldur/Saldura stream in the Italian Central-Eastern Alps, are particularly vulnerable due to their dependence on snow and glacier melt. The Saldur/Saldura catchment (ca. 100 km²), one of the driest areas of the Alps and part of an LTSER platform, is a unique study area due to its dry conditions, low anthropogenic stressors, and the presence of a glacier that sustains the hydrology of this inner-Alpine valley. Since 2010, a long-term biomonitoring program has been assessing the effects of climate and anthropogenic factors - specifically the construction of a small run-of-river (ROR) hydropower plant in 2015 - on stream macroinvertebrate communities. Monthly monitoring during the snow-free period (April-September/October) was initially conducted at three altitudinal sampling sites and was expanded to six sites after the construction of the ROR hydropower plant. This high-resolution temporal dataset allowed us to analyse the spatial and temporal dynamics of macroinvertebrate assemblages in response to natural and anthropogenic drivers. Our findings provide insights into the key dynamics shaping macroinvertebrate communities, highlighting the predominant influence of seasonal melting processes driven by snow and glacier dynamics on their structural and taxonomic characteristics. Increased runoff during peak melt periods corresponds to a decrease in faunal density, taxa richness and functional diversity. Longitudinal gradients also emerged, with taxa distribution patterns reflecting variations in temperature, discharge, and suspended sediment load along the stream. We also observed that seasonal glacial melt dynamics appeared to overshadow the potential impacts of hydropower operations, suggesting that the Saldur/Saldura stream's hydrology and benthic communities remain primarily shaped by climatic drivers. This study highlights the value of long-term, high-resolution monitoring in disentangling the complex interplay between natural processes and anthropogenic factors in sensitive Alpine ecosystems. By combining long-term biomonitoring approaches with advanced statistical analyses, our work demonstrates the resilience of glacier-fed stream macroinvertebrate communities to localised human impacts, while emphasising their vulnerability to climate-induced changes in glacier and snowmelt dynamics. The results contribute to a broader understanding of the ecological implications of small hydropower plants in low-impacted valleys and highlight the importance of sustained monitoring efforts for effective management, conservation and future water scarcity scenarios in Alpine regions.

Macroalgae filling the habitat void following catastrophic losses of seagrass in the Indian River Lagoon, FL

The Indian River Lagoon (IRL) on Florida’s east-central coast is a highly eutrophic, urbanized estuary where, beginning in 2011, multiple harmful phytoplankton blooms were followed by catastrophic seagrass losses. Since then, in many locations where seagrass was lost, the rhizophytic green macroalga Caulerpa prolifera has become the dominant benthic cover. Although the habitat value of C. prolifera compared to the seagrass Halodule wrightii was assessed in the IRL during the late 1980s, there is no information regarding its current habitat value following the catastrophic losses of seagrass. Therefore, the habitat function of C. prolifera in the IRL was assessed during a period of very low seagrass cover by quantitively sampling epifauna inhabiting this macroalga. The benthic habitat cover and faunal composition of four C. prolifera sites in the IRL were determined between 2020–2021. Benthic cover varied by site and event with variable % cover of C. prolifera overall. The faunal composition of C. prolifera was similar to what was previously observed for H. wrightii in the IRL, however faunal densities were significantly lower than historic estimates, which is critical information for resource managers. Incidentally sampled red drift macroalgae supported epifaunal species similar to C. prolifera also demonstrating its current habitat value in the IRL. Thus, these macroalgal habitats may be serving as refugia for estuarine fauna in the relative absence of seagrasses, however faunal densities may have declined from historic levels. These findings may be useful to other locations experiencing catastrophic seagrass losses combined with large-scale macroalgal blooms.

Community Structure of Litter Dwelling MacroFauna Across Age-Stratified Rubber Plantations

Forests serve as natural habitats for litter macrofauna, playing a crucial role in sustaining their survival. However, widespread forest conversion into plantations has become increasingly common, while information regarding litter macrofauna and their ecological roles particularly in Indonesia remains limited. This study explores the community structure of litter macrofauna in rubber plantations of varying ages (11 and 23 years) to assess how plantation age influences their ecological roles in Indonesia. The research was conducted in two rubber plantations, selected using a stratified sampling method based on tree age. Litter samples were gathered through the litterbag method, and the fauna were extracted using the Berlese-Tullgren funnel technique. Data analysis focused on measuring density, diversity index (H'), evenness index, and dominance index. A total of 18 species of litter macrofauna were identified, with 16 species present in the 11-year-old plantation and 9 species in the 23-year-old plantation. The younger plantation exhibited a greater density of fauna (4.02 individuals per litterbag) compared to the older plantation (2.29 individuals per litterbag). However, the diversity index was lower in the younger plantation (H' = 1.52), while the dominance index was higher (D = 0.45), in contrast to the older plantation (H' = 1.79, D = 0.18). These findings suggest that plantation age has a significant impact on the structure of litter macrofauna communities. While younger plantations support a higher density of fauna, they also demonstrate lower species diversity due to increased dominance, indicating a lack of ecological balance. This research underscores the importance of accounting for plantation age in the management of agroecosystems. It is recommended that older rubber plantations, such as those that are 23 years old, be considered for replanting to improve ecosystem function and restore faunal diversity, thereby promoting long-term productivity.

Restoring Halodule uninervis: evaluating planting methods and biodiversity

Seagrass provides a crucial habitat for numerous marine species and serves as a vital food source for endangered species, like dugongs. While extensive research on restoration has been conducted on certain temperate and slow‐growing climax seagrass species, limited attention has been given to tropical pioneer species. This study aimed to assess and compare two restoration methods for the pioneer seagrass Halodule uninervis and evaluate their potential for biodiversity recovery after planting. We conducted a field experiment at subtropical Inhaca Island, southern Mozambique, testing the efficiency of two planting methods (plugs and single shoots) and two planting densities (~100 and ~300 shoots/m2). We monitored seagrass shoot density in two sites for 16 months, and benthic macrofauna density for 12 months. Results demonstrated that seagrass could grow in all combinations of planting methods and densities in both sites. Specifically, the single shoot method at the high‐density treatment proved the most effective, resulting in approximately 1000 shoots/m2 within a year. Faunal densities, primarily dominated by polychaetes followed by malacostraca, bivalves, and gastropods, indicated rapid colonization of the planted areas, especially in the high‐density treatments. Our findings suggest that restoring H. uninervis is feasible using the two tested planting methods. This is particularly significant because H. uninervis is a preferred dugong food source, and its decline due to anthropogenic activities could be reversed through restoration efforts. Nonetheless, conserving existing seagrass should be the primary focus, and restoration approaches should be employed as a valuable tool for managing coastal areas.

Coupling between landward and seaward fringes of sandy beaches: algal deposits on the upper beach influence biogeochemistry and faunal assemblages in the swash zone

Energy subsidies from the sea typically underpin ocean-exposed sandy beach ecosystems. Strandings of detached macroalgae – ‘wrack’ – can be a spectacular form of such cross-ecosystem transfers of organic matter that sustain consumers in the recipient shore system; this has given rise to a model of wrack promoting the diversity and abundance of invertebrates, with scaling effects on upper trophic levels.However, most wrack is often wave-cast to the upper beach, whereas a distinct part of the shore fauna is limited to the ocean fringe of beaches – the ‘swash zone’. This has the potential to create a spatial asymmetry between the location of subsidies (concentrated at the landwards fringe) and the location of some of the putative recipients distributed at the ocean fringe.Here, we tested whether the fauna of the swash zone can benefit from wrack subsidies, by sampling fauna and algal deposits on a range of beaches in NW Spain. We also measured the potential functional link between algal wrack and nutrients released from wrack during decay.Wrack decay increased nutrient concentrations, and it is the combination of wrack cover, nutrient levels, and sediment coarseness that jointly drove variation in the assemblage structure of the swash fauna among beaches. Similarly, the density of the swash fauna and species richness increased markedly at higher nutrient levels and wrack cover.Filter feeders were an important compartment in the food web of the swash macrofauna; we hypothesize that wrack deposits in the upper beach enhance food availability for this trophic guild via increasing nutrients in the water column, stimulating primary production and providing particulate organic matter derived from algal decay. Besides, several polychaetes and peracarid species function as secondary consumers and detritus feeders that plausibly benefit, directly or indirectly, on the particulate organic matter that accumulates on the sediment surface or percolates into the interstitial environment.These findings expand the ‘wrack enhancement’ model to include the promotion of consumers at the ocean edge of sandy shores; it also contains a cross-shore linkage via decomposition processes that favourably change the nutrient regime across all the beach face and thereby couple the swash zone with the upper strandline.

Assessing the Population of Weeds, Insects and Predators in the Organic and Conventional Fields in Coimbatore District, Tamil Nadu, India

In the present investigation an attempt was made to assess the frequency, density, abundance, relative frequency, relative density, relative abundance and important value index of flora and fauna in both the fields of organic and conventional methods of farming in Coimbatore district. The survey was conducted in the fields in three different locations in Coimbatore district, 1) Navakkarai, 2) Cheran nagar and 3) Chinnapampalayam near Anamalai. Weed species and Predators like spiders, ladybird bettles and grasshoppers were predominant in organic fields and earthworms were found to be more in organic fields. Pest management in organic farming depends mainly on crop husbandry and biological control. The prohibition of synthetic fertilizers and pesticides leads to conservation of natural enemies including predators and parasitoids.

Climate change mitigation through biodiversity conservation of wild nutmeg (Myristica spp.) and its habitat (case study in Halmahera Forest, North Maluku)

Changes in the growing environment (habitat), including the habitat of wild nutmeg (Myristica spp.) due to deforestation, land degradation due to mining, erosion of soil fertility, reduced density of flora, fauna, and microorganisms can increase the risk of climate change. The role of the wild nutmeg plant environment is that its canopy can absorb CO2 from the air, and its roots effectively store water and prevent erosion so that it can mitigate climate change. Vegetation analysis is used as an approach to climate change mitigation through managing wild nutmeg habitat biodiversity as a single function of the Halmahera forest against the impacts of climate change. The results of vegetation studies on the natural habitat of wild nutmeg have shown that the composition and structure of the natural habitat vegetation of wild nutmeg in the Halmahera forest have been disturbed although still in the moderate category. The composition and structure of the natural habitat vegetation of wild nutmeg (Myristica spp.) in the Halmahera forest, North Maluku with abundant diversity and high species richness can play a role in mitigating climate change as long as the biodiversity of vegetation in this area is maintained stable. Further studies based on this research can provide deeper insight into wild nutmeg conservation strategies and their role in mitigating climate change.

Vegetation condition and tourism suitability of natural mangrove in Bagek Kembar, Lombok, Indonesia

Abstract. Hadiprayitno G, Suana IW, Santoso D, Japa L, Suyantri E, Wirajagat GC, Syazali M, Ilhamdi ML, Kawirian RR. 2024. Vegetation condition and tourism suitability of natural mangrove in Bagek Kembar, Lombok, Indonesia. Biodiversitas 25: 3703-3711. The Bagek Kembar Essential Ecosystem area is one of several mangrove-based tourist destinations in Lombok, Indonesia. This area features a natural mangrove forest zone amidst rehabilitated mangrove forests from former community ponds. This study aimed to understand the vegetation structure and composition of natural mangrove, the level of damage and their suitability for ecotourism. Data were collected from March to May 2023 by establishing eleven research transects. Trunk diameter and tree height were measured and canopy cover was analyzed using the Hemispherical Photography Method. A vegetation analysis was used to describe the mangrove community structure and composition. Level of damage was assessed using density and coverage parameters of mangrove vegetation while suitability for tourism was assessed using the tourism suitability index with parameters including the number of species, density and thickness of mangroves, tides, and fauna associated with the mangrove ecosystem. Eight mangrove species from five families were identified with the dominance of three species: Avicennia marina (Forssk.) Vierh., Rhizophora mucronata Lam., and Rhizophora stylosa Griffith which spread across all transects. High variations in stem diameter and height indicated that the mangroves originated from natural succession. The natural mangrove forest zone in Bagek Kembar Essential Ecosystem area is classified as good based on the average density and percentage of canopy cover and is deemed very suitable for ecotourism development.

Habitat area more consistently affects seagrass faunal communities than fragmentation per se

Abstract Seminal ecological theories, island biogeography and the single large or several small (SLOSS) reserve debate, examine whether large contiguous habitats conserve biodiversity better than multiple smaller patches. Today, delineating the ecological effects of habitat area versus configuration in a fragmentation context remains difficult, and often confounds efforts to understand proximate and ultimate drivers of community change in response to habitat alteration. We examined how the major components of fragmentation, habitat division versus area loss, independently influence faunal communities using landscapes constructed from artificial seagrass at scales relevant for juvenile estuarine nekton. We deployed 25 unique, 234‐m2 landscapes designed along orthogonal axes: habitat percent cover (i.e., area) and fragmentation per se (i.e., patchiness) to examine their effects on faunal density, community composition, and probability of bait‐assay consumption. Faunal sampling occurred in both artificial seagrass and interspaced sandflat matrix. We also examined whether larval‐settler density drove faunal density patterns across landscapes. Further, we assessed the relative importance of landscape‐scale parameters versus fine‐scale complexity–canopy height and epiphyte biomass–in determining faunal densities. We most consistently observed increasing epibenthic fish and macroinvertebrate density with increasing seagrass percent cover. Fragmentation per se only negatively affected epibenthic faunal density within the matrix at low seagrass coverage. Bait consumption increased with seagrass cover, suggesting larger habitats are relative foraging hotspots. Alternatively, benthopelagic fish density was unaffected by habitat parameters, reflecting lower seagrass reliance, or increased matrix tolerance. Community compositions did not vary across landscapes, suggesting that abundant species used landscapes indiscriminately. Finally, the relative importance of habitat parameters shifted across faunal guilds and life stages. Landscape percent cover most affected epibenthic faunal density, but not benthopelagic fish density, and neither pattern was related to settler density. Further, only fine‐scale complexity influenced settler densities. Collectively, our results indicate habitat area is a primary, positive driver of faunal densities and generalist consumption, and therefore should be prioritized in seagrass conservation. However, sampling across spatial scales and habitat types revealed nuances in habitat use patterns among faunal guilds and life stages that were not solely area‐dependent, illustrating that a variety of landscape configurations support essential nursery functions.

A preliminary recording of insects on the island of Farwa Northwest of Libya

The study aimed to present the first record of insect families in Farwa Island. Farwa Island is the largest and most important island in Libya; located in Northern west part of Libya in the Mediterranean, its insect fauna is poorly studied. Short time intensive collection of insect samples was conducted in four areas (mouth of the valley, bay of containers, center of the Island, and Ras-Attalgha) in February, March and April 2021. Different methods were used for insect collection, sorting, preservation and later identification to the lowest taxonomic level and verification. 9 orders, 31 families, 40 genera and 58 insect species were collected in the study; the center of the Island had the highest numerical density and diversity of insect fauna due to its diverse vegetation compared to other areas. Diverse suitable habitats and absent insect control measures provided suitable environmental conditions for insects breeding, feeding and hiding from enemies. This study constitutes the first comprehensive survey of insect fauna on Farwa Island and adds significant value to the ongoing assessment of insect diversity in Libya. A long-term study has to be conducted to investigate detailed information about the abundance and diversity of insects and other arthropods on Farwa Island.

Spatial and temporal variability of fouling communities on oyster spat collectors at Inhaca Island Southern Mozambique: Exploring the influence on recruitment of the oysters Pinctada capensis and Saccostrea cucullata

Spatial and temporal variability of fouling communities on oyster spat collectors at Inhaca Island Southern Mozambique: Exploring the influence on recruitment of the oysters Pinctada capensis and Saccostrea cucullata

Variability in zoobenthic blue carbon storage across a southern polar gradient

Variability in zoobenthic blue carbon storage across a southern polar gradient

Multifaceted leaf litter traits shape soil fauna communities: Evidence from subtropical monocultural plantations

Multifaceted leaf litter traits shape soil fauna communities: Evidence from subtropical monocultural plantations

Elevated fish densities extend kilometres from oil and gas platforms.

Thousands of offshore oil and gas platforms have been installed throughout the world's oceans and more structures are being installed as part of the transition to renewable energy. These structures increase the availability of ecological niches by providing hard substrate in midwater and complex 3D habitat on the seafloor. This can lead to 'hotspots' of biodiversity, or increased densities of flora and fauna, which potentially spill over into the local area. However, the distances over which these higher densities extend (the 'range of influence') can be highly variable. Fish aggregate at such structures, but the range of influence and any implications for wider fish populations, are unclear. We investigated the relationship between fish and platform areal densities using high resolution fisheries acoustic data. Data were collected in the waters surrounding the vessel exclusions zones around 16 oil and gas platforms in the North Sea, and throughout the wider area. We estimated densities of schooling fish using echo-integration, and densities of non-schooling fish using echo-counting. At 10 platforms, non-schooling fish densities were elevated near the platform relative to background levels in the equivalent wider area. The range of influence, defined here as the range to which fish densities were elevated above background, varied from 0.8 to 23 km. In areas of high platform density, fish schools were encountered more often, and non-schooling fish densities were higher, when controlling for other sources of environmental variation. This is the first time such long-range effects have been identified; previously, ranges of influence have been reported in the order of just 10s-100s of metres. These findings suggest that the environmental impact of these structures may extend further than previously thought, which may be relevant in the context of upcoming management decisions around the decommissioning of these structures.

Temperature Mainly Determined the Seasonal Variations in Soil Faunal Communities in Semiarid Areas

The implementation of the Grain for Green Project has increased vegetation coverage and provided suitable habitats and food resources for soil fauna, thereby promoting the development of soil faunal communities. Studying seasonal variations in soil fauna communities in different vegetation areas can improve our understanding of the mechanisms that drive soil fauna recovery. We selected five typical artificially restored vegetation habitats, including Populus simonii (POS), Pinus tabulaeformis (PIT), Caragana korshinskii (CAK), Stipa bungeana (STB), and Medicago sativa (MES), and one farmland (Zea mays, FAL) habitat on the Loess Plateau. In this study, soil fauna communities and environmental factors were investigated during spring (May), summer (August), and autumn (November). Among the habitats, the STB habitat had the largest seasonal variation in soil faunal density (from 1173 ind·m−2 in May to 10,743 ind·m−2 in August), and the FAL habitat had the smallest (from 2827 ind·m−2 in August to 5550 ind·m−2 in November). Among the restored vegetation habitats, Acarina (44.89–88.56%) had the highest relative abundance of all taxa. The redundancy analysis (RDA) results showed that among the factors driving seasonal variation in soil animal communities, temperature (47.41%) was the most important, followed by precipitation (22.60%). In addition, the dominant groups, Acarina and Collembola, played an influential role in seasonal variations in soil faunal density. Temperature mainly determined the seasonal variations in soil faunal communities. Seasonal factors should be considered when conducting soil fauna research, as they contribute to biodiversity conservation and regional ecological management in the Loess Plateau.

The Bougara dam’s water quality assessment using macroinvertebrates benthic indices

The benthic macroinvertebrate communities along with the physicochemical variables in Bougara dam waters (Nahr Ouassel river) downstream of a dam North-western of Algeria, were recorded from three sampling sites during January to May 2022. All the physicochemical parameters were highest in the first station (temperature, pH, conductivity, BOD and COD) while they were slightly lower in the second station and low in the third station. A total of 13 species, belonging to 10 families of 7 orders of benthic macroinvertebrates were recorded. With a great domination of insects. The maximum density of benthic fauna was recorded from the site nearest to the dam exit. These results were confirmed by the benthic indices of macroinvertebrates where the recommendations are to clean the first highly polluted station and to keep monitoring the other remaining stations moderately polluted.

Diversity and density relationships between lebensspuren and tracemaking organisms: a study case from abyssal northwest Pacific

Abstract. In the deep sea, interactions between benthic fauna and seafloor sediment primarily occur through bioturbation that can be preserved as traces (i.e. lebensspuren). Lebensspuren are common features of deep-sea landscapes and are more abundant than the organisms that produce them (i.e. tracemakers), rendering lebensspuren promising proxies for inferring biodiversity. The density and diversity relationships between lebensspuren and benthic fauna remain unclear, and contradicting correlations have been proposed (i.e. negative, positive, or even null correlations). To approach these variable correlations, lebensspuren and benthic fauna were characterized taxonomically at eight deep-sea stations in the Kuril-Kamchatka Trench area, together with two novel categories: tracemakers (specific epibenthic fauna that produce these traces) and degrading fauna (benthic fauna that can erase lebensspuren). No general correlation (overall study area) was observed between diversities of lebensspuren, tracemakers, degrading fauna, and fauna. However, a diversity correlation was observed at specific stations, showing both negative and positive correlations depending on: (1) the number of unknown tracemakers (especially significant for dwelling lebensspuren); (2) the lebensspuren with multiple origins; and (3) tracemakers that can produce different lebensspuren. Lebensspuren and faunal density were not correlated. However, lebensspuren density was either positively or negatively correlated with tracemaker densities, depending on the lebensspuren morphotypes. A positive correlation was observed for resting lebensspuren (e.g. ophiuroid impressions, Actiniaria circular impressions), while negative correlations were observed for locomotion-feeding lebensspuren (e.g. echinoid trails). In conclusion, lebensspuren diversity may be a good proxy for tracemaker biodiversity when the lebensspuren–tracemaker relationship can be reliable characterized. Lebensspuren–density correlations vary depending on the specific lebensspuren residence time, tracemaker density, and associated behaviour (rate of movement). Overall, we suggest that lebensspuren density and diversity correlations should be studied with tracemakers rather than with general benthic fauna. On a global scale, abiotic (e.g. hydrodynamics, substrate consistency) and other biotic factors (e.g. microbial degradation) may also play an important role.

Impact Of Water Current Velocity In Structuring Benthic Macroinvertebrate Community In Ramganga River, India

The objective of this study was to investigate how the speed of water flow affects the composition of benthic macro-invertebrate communities in the Ramganga River, located in the Himalayas. Over a period spanning from October 2014 to March 2015, samples were collected from eight different locations along the river, ranging from its source to its mouth (designated as S1 to S8). A total of 160 samples of invertebrates were collected from each station, covering a spectrum of current velocities. These velocities were classified into five categories: extremely low (type I, 0-15 cms-1 ), low (type II, 15-30 cms-1 ), moderate (type III, 30-45 cms-1 ), moderate (type IV, 45-60 cms-1 ), and high (type V, >60 cms-1 ). The mean density of invertebrate fauna exhibited an increase from type I (214.0±104.6) to type III (545.7±361.3), followed by a decrease in type IV (22.8±5.7), and then a subsequent increase in type V (315.6±250.6). However, these fluctuations did not demonstrate a significant relationship. In total, 34 different taxa were identified across all sampling stations. The highest number of taxa (22) was observed in type III, while the lowest (8) was found in type IV. Among these taxa, Glossoscolecidae was most abundant in areas with type I velocity, Simulidae in type II, Leptoceridae in types III and V, and Psephenidae in type IV. Furthermore, Principal Component Analysis (PCA) was employed to elucidate the characteristic taxa associated with each velocity type. The results highlighted that mild velocity (type III) was particularly crucial in fostering maximum density and species richness within the benthic macro-invertebrate communities

The Role of a Faunal Engineer, Geukensia demissa, in Modifying Carbon and Nitrogen Regulation Services in Salt Marshes

Abstract Interest in leveraging suspension feeders, such as marine bivalves, to exert top‐down control on organic matter (OM) loading in estuaries is gaining momentum. Not only can these faunal engineers alleviate the consequences of nutrient pollution, but they may also bolster the critical blue carbon services provided by coastal ecosystems—a potential dual, mitigating effect on cultural eutrophication and climate change. Ribbed mussels, Geukensia demissa, offer a useful model for assessing faunally driven carbon (C) and nitrogen (N) processes in these systems and their relationships with faunal density. Combining bulk geochemical analyses with Bayesian stable isotope mixing model frameworks (MixSIAR), we quantified the effect of mussels on the source and amount of organic C and N deposited to the benthic floor (i.e., sedimentation), accumulated in surface sediments, and stored in aboveground Spartina alterniflora in Georgia salt marshes. Relative to areas without mussels, mussel presence shifted the source of deposited and accumulated OM to a more allochthonous makeup; amplified the amount of deposited, but not accumulated, allochthonous and autochthonous OM; and enhanced aboveground storage of C and N. Both sources of OM accumulated in sediments as well as standing stocks of C and N were highly and positively correlated with local mussel density (ind. m−2) but unrelated to neighboring mussel density (ind. ∼25 m−2) in adjacent, non‐mussel areas. This work provides new evidence that suspension feeders, through their faunal engineering activities, can interact powerfully and synergistically with primary producers to enhance the blue carbon services of marshes and counteract coastal eutrophication.