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Recent studies in terrestrial, plant-dominated systems have shown that reductions in diversity can affect essential ecosystem processes, especially productivity. however, the exact form of the relationship between diversity and ecosystem functions remains unknown, as does the relevance of these studies to other systems. We studied the relationships...
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... it is apparent that species composition between the low, medium, and high biomass treatments were very similar; biomass differences are predominantly due to differences in the abundances of those present. Table 3 shows the mean and total number of species sampled from each of the treatments, together with the total and mean numbers of species from each trophic group. Feeding modes are those proposed by Fauchald and Jumars (1979). ...
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... modes are those proposed by Fauchald and Jumars (1979). Since macrofaunal feeding mode determines how a species reworks the sediment, and therefore reflects its role within the benthic ecosystem, trophic mode is used to indicate species' functional roles in this study (Table 3). A total of five macrofaunal feeding modes were sampled, with some species, such as Macoma balthica, exhibiting more than one feeding mode. ...
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... conclusions ob- tained from this large-scale study concur with those in the present study in suggesting that certain ecosystem processes may be insensitive to changes in species rich- ness. The impacts of losing a functional group, which resulted in significant effects on ecosystem perfor- mance in Elmgren's study, cannot be assessed in this study since all functional groups were present in all diversity treatments (Table 3). Further support for the importance of functional groups, rather than species per se, comes from the small-scale mesocosm studies of Emmerson and Raffaelli (2000). ...
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... Menurut Ranjan et al. (2010) bahwa komposisi utama sedimen mangrove adalah lumpur, tanah liat dan pasir. Hutan mangrove Indonesia yang tumbuh subur pada sedimen lumpur maupun pasir dapat dijumpai di wilayah Pulau Sumatera, Kalimantan dan Irian Jaya (Sukardjo, 1984), dimana keadaan sedimen mangrove yang banyak mengandung lumpur, biasanya lebih tinggi mengandung bahan organiknya sehingga merupakan habitat yang sesuai bagi kehidupan gastropoda (Bolam et al. 2002). Hal ini juga didukung oleh pernyataan Suratissa dan Rathnayake (2017) serta Salmo et al. (2017) bahwa gastropoda laut umumnya ditemukan di berbagai habitat, salah satunya adalah pantai berlumpur mangrove. ...
The purposes of the reasearch that was conducted on July 2022 are to determine the biodiversity, composition, density, community index, correlation and contribution of gastropods on 18 year post tsunami and 16 year coastal rehabilitation in research observation of Banda Aceh. The method used is purposive sampling with 4 observation stations. Gastropods were collected using a quadratic transect perpendicular to the shoreline. PCA analysis was carried out to determine the level of contribution of gastropod species based on observation stations, while SIMPER and CA analyzes were carried out to compare and classify gastropod communities. A total of 8 families, 8 genera, 10 species and 6945 ind gastropods were found with densities ranging from 37.55 – 136.60 ind/m2. The highest diversity index was found at Station II (0.63), the highest uniformity index was found at Station III (0.86) and the highest dominance index was found at Station I (0.99). Gastropods Nerita planospira, Cassidula aurisfelis, C. nucleus, Sphaerassiminea miniata and Oncidium sp. closely related to Rhizophora mucronata and Avicennia alba growing on muddy substrates, while Morula iostoma, Cerithidea cingulata, Littoraria melanostoma, Nassarius olivaceus and L. scabra were closely related to R. mucronata growing on sandy mud substrates. Furthermore, C. cingulata species contributed at Stations I and IV, while C. aurisfelis species contributed at Stations II and III. Kajian dilakukan pada bulan Juli 2022 yang bertujuan untuk mengetahui biodiversitas, komposisi, kepadatan, indeks komunitas serta keterkaitan dan kontribusi gastropoda terhadap stasiun pengamatan pasca 18 tahun tsunami dan 16 tahun rehabilitasi pantai di Kota Banda Aceh. Metode yang digunakan adalah purposive sampling dengan 4 stasiun pengamatan. Gastropoda dikumpulkan menggunakan transek kuadrat yang tegak lurus garis pantai. Analisis PCA dilakukan untuk mengetahui tingkat kontribusi spesies gastropoda berdasarkan stasiun pengamatan, sedangkan analisis SIMPER dan CA dilakukan untuk membandingkan serta mengklasifikasikan komunitas gastropodanya. Sebanyak 8 famili, 8 genus, 10 spesies dan 6945 ind gastropoda ditemukan dengan komposisi gastropoda antar stasiun pengamatannya berbeda nyata (p = 0.000) serta kepadatan gastropodanya berkisar antara 37.55 – 136.60 ind/m2. Indeks keanekaragaman tertinggi ditemukan pada Stasiun II (0.63), indeks keseragaman tertinggi ditemukan pada Stasiun III (0.86) dan indeks dominasi tertinggi ditemukan pada Stasiun I (0.99). Gastropoda Nerita planospira, Cassidula aurisfelis, C. nucleus, Sphaerassiminea miniata dan Oncidium sp. berkaitan erat dengan Stasiun II dan III (substratnya berlumpur), sedangkan Morula iostoma, Cerithidea cingulata, Littoraria melanostoma, Nassarius olivaceus dan L. scabra berkaitan erat dengan Stasiun I dan IV (substratnya lumpur berpasir). Selanjutnya, spesies C. cingulata memiliki kontribusi di Stasiun I maupun IV, sedangkan spesies C. aurisfelis memiliki kontribusi di Stasiun II maupun III.
... The type of substrate found in the mangrove area of Kutang Beach are sandy mud and rocky. The muddy substrate contains high organic matter so it is suitable for the habitat of the gastropod community (Bolam et al 2002). Based on the presence of gastropod species at the six stations, the highest number of species was found in the dense mangrove area (Station III), 20 species. ...
Gastropods are one of the communities that utilize the mangrove ecosystem as their habitat. This study aimed to identify gastropods as well as to analyze the community structure of gastropods and analyze their habitat characteristics, in the mangrove area of Kutang Beach, Lamongan Indonesia. Sampling was conducted during the lowest tide using the quadrant-transect method. The Gastropods were identified based on morphological characters. Community structure was analyzed descriptively and quantitatively, based on seven parameters, namely: density (D), relative abundance (KR%), relative frequency (FR%), importance value index (INP%), diversity index (H'), dominance index (C) and evenness index (E). The results revealed that on the Kutang Beach there were 30 species of gastropods belonging to several families. Littoraria articulata (Littorinidae family) had the highest density, D=1.83 ind m-2 , with a relative abundance of KR=19.88%, a relative frequency of FR=7.59% and an importance value index of INP=27.47%. The diversity index 1<H'<3 was moderate, the low dominance index C<0.5 indicated the absence of dominance between species and the evenness index 0.6<E<1 was high, indicating a relatively balanced distribution between species. Gastropods' habitat characteristics in the mangrove ecosystem were: a sandy mud substrate, a temperature of 29±0.00°C; a pH of 7.86±0.00 and a salinity of 3±0.58‰.
... Despite some contradictory results, several studies conducted in different marine systems have shown that macrofauna diversity influences, both directly (grazing) and indirectly (biomass production), a variety of ecosystem processes and properties such as biogeochemical cycles and pools of OM (Baldrighi et al., 2017;Bolam et al., 2002;Duffy et al., 2003). Experimental studies using organisms from different trophic/functional groups (e.g., decomposers, ciliates, epigrazers) suggest that a more diverse consumer assemblage can enhance secondary production (Duffy et al., 2005;Gamfeldt et al., 2005;Naeem, 2002). ...
... Therefore, although variance partitioning results implied that some benthic environmental factors affect secondary production, the extreme lower and upper limits for seagrass productivity were naturally controlled by macrofauna biodiversity (Figure 3). The exponential shape of the relationship between macrofauna biodiversity and seagrass secondary production is different from the typically saturating relationship observed in laboratory experiments (Bolam et al., 2002;Duffy et al., 2003;Mora et al., 2014). The strength and the nature of biodiversity and ecosystem functioning relationships can differ broadly among habitats and between natural ecosystems and laboratory experiments (Hector et al., 2007;Mora et al., 2014). ...
Coastal vegetated habitats such as seagrasses are known to play a critical role in carbon cycling and the potential to mitigate climate change, as blue carbon habitats have been repeatedly highlighted. However, little information is known about the role of associated macrofauna communities on the dynamics of critical processes of seagrass carbon metabolism (e.g., respiration, turnover, and production). We conducted a field study across a spatial gradient of seagrass meadows involving variable environmental conditions and macrobenthic diversity to investigate (1) the relationship between macrofauna biodiversity and secondary production (i.e., consumer incorporation of organic matter per time unit), and (2) the role of macrofauna communities in seagrass organic carbon metabolism (i.e., respiration and primary production). We show that, although several environmental factors influence secondary production, macrofauna biodiversity controls the range of local seagrass secondary production. We demonstrate that macrofauna respiration rates were responsible for almost 40% of the overall seafloor community respiration. Macrofauna represented on average >25% of the total benthic organic C stocks, high secondary production that is likely to become available to upper trophic levels of the coastal food web. Our findings support the role of macrofauna biodiversity in maintaining productive ecosystems, implying that biodiversity loss due to ongoing environmental change yields less productive seagrass ecosystems. Therefore, the assessment of carbon dynamics in coastal habitats should include associated macrofauna biodiversity elements if we aim to obtain robust estimates of global carbon budgets required to implement management actions for the sustainable functioning of the world's coasts.
... The distribution of functional traits in a community can be a better indicator of ecosystem functioning than assemblage structure, including species abundance, richness and other metrics (e.g., Bolam et al., 2002). For instance, different species can have similar traits, thus performing similar functions. ...
Function in ecology can be understood as the role that each component plays in the surrounding environment. It can be studied through the functional traits of organisms and depends on variations of abundance in time and space. Nevertheless, traits should be clearly associated with functions. The functions performed by estuarine macrofauna along estuarine gradients and its variation in time are scarcely studied. We expected that the functional structure (i.e., the set of functions in a site) would not change significantly over estuarine gradients, even with changes in taxonomic composition, since different taxa may have similar traits, allowing the performance of the same functions. We used polychaete assemblages along three tropical estuaries sampled four different times, to test for differences in functional intensity between estuarine salinity zones (Venice system). From a literature search we selected the most frequent ecological functions performed by estuarine benthic assemblages and we explicitly established which polychaete functional traits, or combinations of traits, were directly related to these functions. Nutrient cycling, bioturbation and fragmentation of organic matter were the most frequent functions. We discovered that the last two were present throughout the entire salinity gradient (i.e., along different salinity zones) but with different intensities. The intensity of functions may also show significant variability in time. Nutrient cycling and fragmentation of organic matter showed strong variation among estuarine zones. Using traits explicitly associated with ecological functions is necessary to investigate function and function intensity. Future studies should investigate how precisely traits may alter specific environmental characteristics and ecosystem properties.
... Benthic organisms with little or no mobility have been widely used in aquatic environmental impact assessment and monitoring (Rosenberg and Resh, 1993). As a matter of fact, they are sensitive sensors of physical and chemical changes undergone by aquatic systems in general and benthic systems in particular (Bolam et al., 2002). They are closely associated with the floor of aquatic systems, hence can hardly avoid deteriorated conditions of water or sediment. ...
To analyse the extent of disturbances and determine the state of health of aquatic systems, the integration of several biological effects at different levels of biological organization has been used. One of the most valuable methods of biological effect measurements is the use of ecological surveys at community and population levels. In this study, the distributional evaluation of benthic biocoenosis was undertaken to determine site-specific differences in community assemblage in relation to environmental status of the study sites. Three study locations (Okobaba, Iddo and Tin Can Island) in the western side of the Lagos Lagoon with highest concentrations of human activities were selected. These sites represent areas directly affected by major anthropogenic discharge into the Lagos Lagoon. Samples were collected for six consecutive months (March and August 2014). There was great variation in parameters investigated among the study sites. The concentrations of dissolved oxygen in surface water varied from 3.0- 4.5 mg/L. Chlorophyll a in surface water fluctuated from 0.12- 2.01 mg/L whereas, in sediment values varied from 0.14-1.32 mg/g. Biomass of microphytobenthos (MPB) varied from 1.4-13.2 g. Of the total 841 MPB cells collected the highest population was recorded in Okobaba. Twelve MPB taxa were recorded in the study area. The most important species in terms of numerical abundance was Oscillatoria sp. This organism occurred in all the study stations and recorded a total of 113 cells in the study stretch. A major feature of the population distribution of the MPB taxa in this study is the occurrence of higher number of cells at Okobaba. The number of individuals and the distribution of BMF taxa varied greatly from one study location to another. Of the total 801 individuals collected, 398 were recorded at Okobaba, 316 occurred at Tin Can Island and 18 at Iddo. Unlike the case of MPB organisms, a fewer number of BMF taxa were recorded in the study area. The most important MBF taxon in terms of numerical abundance was Pachymelania aurita. This organism occurred in all the study sites and recorded a total of 162 individuals thereby constituting 20% of the total MBF population collected. The benthic community observed in this study was characterized by low number of individuals and the species of MPB and MBF recorded are known opportunistic species common in stressed environments.
... individual density) may be more determinant than production (i.e. biomass density) in benthic functional patterns as concluded by Bolam et al. (2002). Nevertheless, as shown in the high-dynamics pattern, total biomass community, negatively correlated to the first RLQ axis, can be indicative of a stress effect on biological production ( Table 3). ...
Biological traits of benthic macroinvertebrates from a large area of the North Sea soft sediments were used to explore habitat occupancy within seascapes of contrasting hydrodynamics. The area, the Dutch sector of the North Sea, is mainly composed of 2 habitats: shallow dynamic bottoms of heterogeneous geomorphologies and deep homogeneous muddy bottoms. Higher within-habitat heterogeneity was hypothesized to more specifically select benthic life strategies according to environmental filtering, i.e. through the action of abiotic forces. Functional community patterns were explored through the RLQ method, which relates habitat and trait variables, at different spatial scales of specific seascape heterogeneity, and functional diversity indices were used to shed light on community assembly mechanisms. Locally, 3 associations between habitat characteristics and biological traits were shown to correspond with predictions of life history theories, whereas only 2 emerged when considering all types of seascapes. This spatial scaledependence was explained by abiotic alternations masked over the larger scale at which all the existing strategies could not be properly disentangled. The relative composition in strategies obeyed specific assembly rules as identified by functional diversity indices. Seascape geomorphology was locally discriminant of functional patterns, and could account for biodiversification, much beyond basic taxonomic counts. Whereas habitats of higher physical stability hosted the taxonomically richest communities, stress or disturbance frequency increased functional variations within communities due to different strategist habitat occupancies. This study proposes a generic mechanism of benthic community structuring in soft sediment shelves.</p
... Such areas are classified as highly eutrophic (Robertson et al. 2016,b) and generally harbor depauperate biological communities due to reduced habitat availability and quality (Robertson et al. 2016, b,c). These effects also limit foraging habitat for fish, birds and macroinvertebrates (Bolam et al. (2002). We note that benthic conditions could deteriorate beyond those associated with "nuisance macroalgae" (e.g., azoic-devoid of invertebrate life-sediments overlain by a bacterial film rather than a macroalgal canopy), but such degraded situations have not been documented in New Zealand intertidal estuaries. ...
Eutrophication of shallow coastal ecosystems often manifests as dense mats of opportunistic macroalgae, degraded underlying sediments and displacement of ecologically important primary producers including seagrass beds. Ecological thresholds of drivers that cause these shifts in ecosystem state are needed to manage eutrophication symptoms before tipping points are crossed. This study quantifies total nitrogen (TN) load
thresholds for abrupt changes in ecologically important seagrass habitat and the appearance of nuisance macroalgae as a function of estimated catchment TN load to shallow, intertidal estuaries in New Zealand. Results indicate that the extents of both macrophyte types are strongly governed by increasing TN load to the estuaries, while total suspended sediment load was not significant alone or as an interaction term. Seagrass extent was unpredictable below a critical TN load envelope (< 50 mg N m−2 d−1), likely because there are additional factors
than TN that influence seagrass cover, but once surpassed, seagrass became restricted to less than 10% of intertidal area or absent. Conversely, nuisance macroalgae was predominantly absent unless TN load exceeded 41.15 ± 21.1 mg N m−2 d−1, expanding in extent by 2.7% of intertidal area for every 50 mg N m−2 d−1 increase above threshold levels. This research underscores the importance of managing diffuse nitrogen inputs to safeguard the structure and function of shallow estuarine ecosystems before tipping points in dominant macrophyte
type are crossed.
... Water depth and resource availability (i.e., quality and quantity) have a great influence on sediment oxygen demand (SOD) (Mouret et al., 2010;Bourgeois et al., 2017). Functional diversity has profound implications for ecosystems and their functioning (Mermillod-Blondin et al., 2004;Michaud et al., 2006Michaud et al., , 2009Link et al., 2013;Snelgrove et al., 2014) and seems to be more important than the diversity per se (Bolam et al., 2002;Belley and Snelgrove, 2017). As a result of their bioturbation activities (e.g., reworking sediment and bio-irrigation) and their behavior (e.g., feeding, mobility), which generate different levels of disturbance (Biles et al., 2002), infaunal organisms may cyclically enhance oxygen penetration within the sediment, increase oxic respiration, stimulate organic matter degradation and change inorganic nutrient fluxes at the sediment-water interface (Vopel et al., 2003;. ...
The Arctic Ocean is emerging as one of the regions that is most affected by climate change.
A significant increase in precipitation and sea surface water temperatures are expected and
will undeniably lead to a significant loss of sea ice cover. Because of their effects on physicochemical parameters, these changes are expected to directly impact the surface primary producers (sea ice algae and phytoplankton), thereby limiting organic matter input towards the seafloor. It is thus commonly accepted that climate change will affect the distribution, diversity and abundance of benthic communities, due to its impact on environmental parameters (pelagic-benthic coupling and physicochemical parameters), and on ecosystem services and functions (e.g., benthic remineralization). As a consequence, the decrease in sea ice cover, the desalination of the surface layer or the increase in shipping traffic in the Hudson Bay Complex and in the eastern Canadian Arctic will likely lead to major changes in benthic community structure and biogenic structural habitats.
In this context and since the impacts of climate change on benthic arctic ecosystems were
still poorly understood, the objectives of this thesis were to i) describe the diversity and
distribution of epibenthic communities in the Hudson Bay Complex and ii) understand the
effects of climate change on biodiversity and benthic ecosystem functioning. The outcomes
of this thesis allowed us to i) provide the most recent survey on epibenthic organisms in the
Hudson Bay Complex and their relationships with environmental variables; ii) identify
diversity hotspots sensitive to climate change; and iii) document and compare benthic
biodiversity and fluxes within biogenic structures and adjacent bare sediments in the
Canadian Arctic.
A total of 380 taxa have been identified from 46 stations sampled across the Hudson Bay
Complex. Despite the relatively low spatial coverage of our sampling, we estimated that our
survey represented 71% of the taxa present in the Hudson Bay Complex. We showed that
biomass, abundance, diversity and spatial distribution of epibenthic communities were
strongly influenced by substrate, salinity, food supply and sea ice cover. We also showed that
freshwater inputs were responsible for the lowest biomass, abundance and diversity observed along the coasts. In contrast, data collected from polynyas, further offshore, showed strong pelagic-benthic coupling resulting in high productivity in terms of biomass, abundance and diversity. Moreover, hierarchical modeling of species communities highlighted the influence of sea ice and indirectly of sea ice algae on the epibenthic communities occupying the central Hudson Bay. Projections of the structure of epibenthic communities under a RCP4.5 climate scenario revealed that the central Hudson Bay emerges as the most vulnerable area to climate change with a future diversity loss related to the decrease of sea ice. On the contrary, it would appear that coastal areas will serve as refuges and increase the diversity. In addition, our study showed that the presence of biogenic structures in deep habitats improved the trapping of organic matter, leading to a higher density of infauna in these environments compared to bare sediments. Their presence has also been found to enhance sediment nutrient release in the form of nitrates and ammonium. However, our study could not demonstrate these effects in a shallower sponge habitat.
By providing new knowledge on the current and future distribution of epibenthic communities in the Hudson Bay Complex and the benthic ecosystem functioning in habitats
with biogenic structures, results obtained during this thesis will contribute to the designation
of Ecologically and Biologically Significant Areas, as well as to the establishment of Marine
Protected Areas and conservation strategies in the Arctic Ocean.
... However, these observations are dependent on the taxa involved. Artificial structures generally support a lower diversity of organisms than adjacent natural rocky shores (Aguilera et al. 2014;Firth et al. 2013;Moschella et al. 2005;Munsch et al. 2014;Pister 2009;Wilhelmsson and Malm 2008), particularly less of rare species (Bulleri and Chapman 2004;Chapman 2003), resulting in a more homogeneous landscape (Lam et al. 2009) and fewer associated ecosystem services (Bolam et al. 2002;Airoldi et al. 2005). Species found on artificial habitats have lower genetic diversity (Fauvelot et al. 2009;Sammarco et al. 2012), possibly due to reduced reproductive output (Moreira et al. 2007). ...
Decades of coastal urbanisation have replaced many natural shorelines with seawalls. Marine communities have been documented on these replacement habitats, but little is known about the effects of seawall inclination on the diversity and depth distribution of sessile organisms on this artificial substrate. Surveys of hard coral and other sessile communities in Singapore indicated that benthic communities at the deeper zone (− 2 m chart datum) were significantly different between three sloping (about 33° inclination) and three vertical seawalls of similar age. Hard coral communities were significantly different between sloping and vertical seawalls and between 0 m chart datum and − 2 m chart datum. Hard coral communities on sloping seawalls were also significantly more diverse than on vertical seawalls. At both depths, sloping seawalls were dominated by abiota with hard coral comprising appr. 17% of the total surface, while vertical seawalls were dominated by algal assemblage with hard coral comprising appr. 10% of the total surface. Overall, the results showed that sloping seawalls were significantly better at supporting coral communities, likely due to less intensive habitat compression and buffered wave action on them, especially at 0 m chart datum. The need to understand how surface topography affects benthic and coral communities in light of growing coastal urbanisation is also highlighted. This study emphasises how sloping seawalls can support greater marine biodiversity than vertical seawalls.
... Water depth and resource availability (i.e., quality and quantity) have a great influence on sediment oxygen demand (SOD) (Mouret et al., 2010;Bourgeois et al., 2017). Functional diversity has profound implications for ecosystems and their functioning (Mermillod-Blondin et al., 2004;Michaud et al., 2006Michaud et al., , 2009Link et al., 2013a;Snelgrove et al., 2014) and seems to be more important than the diversity per se (Bolam et al., 2002;Belley and Snelgrove, 2017). As a result of their bioturbation activities (e.g., reworking sediment and bioirrigation) and their behavior (e.g., feeding, mobility), which generate different levels of disturbance (Biles et al., 2002) infaunal organisms may cyclically enhance oxygen penetration within the sediment, increase oxic respiration, stimulate organic matter degradation and change inorganic nutrient fluxes at the sediment-water interface (Vopel et al., 2003;. ...
The relationships between infaunal diversity and ecosystem function of biogenic structures in the Eastern Canadian Arctic remain poorly documented. Our study investigated the influence of sponge gardens at the Frobisher Bay site (137 m) and bamboo corals at the Baffin Bay site (1007 m) on the infaunal community structure and benthic ecosystem functioning. The occurrence of both types of biogenic structure type enhanced particular taxa and/or feeding guilds. A large density of suspension filter feeders was observed in bamboo coral sediment, whereas bare sediment exhibited a large proportion of nematodes and deposit-detritus feeders. Sponge gardens’ sediment showed a high proportion of isopods, Paraonidae polychaetes and up/down conveyors whereas bare sediment exhibited a large density of filter feeders. Through incubation cores, we measured ex situ benthic nutrient and oxygen fluxes at the sediment-water interface in each habitat and site. Biogeochemical fluxes varied significantly between habitats in the Baffin Bay site with a significant impact of bamboo coral habitat on nutrient fluxes (nitrate, ammonium, and silicate). Surprisingly, the sediment hosting bamboo corals acted as a source of nitrate and ammonium reaching values similar or higher to the Frobisher site despite the difference in water depth, and thus food supply between the two sites. These significant releases could derive from (i) a high organic matter deposition in bamboo coral habitat, allowed by their erected structure, (ii) a high efficiency of bioturbators (surficial modifiers and burrowers) mixing the surface layer of the sediment, and (iii) the difference in sediment type. Our study highlighted that, compared to its adjacent habitat, the presence of bamboo corals appeared to enhance the infaunal density and nutrient release of its sediment. In contrast, the impact of sponge gardens was not as clear as for bamboo coral habitat, likely due to the relatively significant presence of megabiota in the sponge garden adjacent habitat. Thus, our results based on a relatively small sample size, indicate that the bamboo coral habitat seems to increase the efficiency of deep-benthic ecosystem functioning, while that of sponge garden on the shallow ecosystem functioning remains uncertain.
