Larval Community Research Articles

Climate-driven shifts in decapod larvae assemblages in a temperate estuary

The study examines the complex impact of climatic patterns, driven by the North Atlantic Oscillation (NAO), on regional climate, hydrology, and sea surface temperatures. Focused on the period from 2003 to 2012, the research specifically investigates the influence of thermal variability on decapod larval communities. Monthly zooplanktonic sampling conducted at the Mondego Estuary, Portugal, entrance over a decade revealed the prevalence of Carcinus maenas, Diogenes pugilator, and Pachigrapsus marmoratus larvae. These assemblages displayed notable interannual and seasonal fluctuations, often corresponding with changes in sea surface temperatures. Significant system shifts around 2007, instigated by the large-scale NAO, led to subsequent modifications in sea surface temperature and decapod larvae communities' dynamics. Post-2007, there was an upward trajectory in both species’ abundance and richness. Phenologically during the former period, the community exhibited two abundance peaks, with the earlier peak occurring sooner, attributed to heightened temperatures instead of the unique peak exhibited before 2007. The research further elucidated the occurrences of Marine Heatwaves (MHW) in the region, delving into their temporal progression influenced by the NAO. Although water temperature emerged as a crucial factor influencing decapod larvae communities annually and seasonally, the study did not observe discernible impacts of MHW events on these communities. These communities represent essential trophic links and are crucial for the survival success of adult decapods. Given the rapid pace of climate change and increasing temperatures, it is imperative to assess whether these environmental shifts, particularly in thermal conditions, affect these meroplanktonic communities.

Ladybird (Coleoptera, Coccinellidae) communities on nonnative blue spruce in central Europe

Abstract Blue spruce (Picea pungens) has been planted in urban greenery as an ornamental tree in central Europe for more than 150 years. We investigated whether this nonnative spruce is a convenient habitat for ladybirds (Coleoptera, Coccinellidae). In 2021 and 2022, adults and larvae were sampled in four towns in Slovakia at monthly intervals throughout the growing season, from April to October. We recorded adults of 27 species and larvae of 11 ladybird species. Conifer specialist ladybird species predominated both in adult and larval communities (adults – 9 species, 85.2% of all individuals; larvae – 7 species, 92.1% of all individuals). Exochomus quadripustulatus and Aphidecta obliterata were the most common in adult (31.8% and 33.5% of all individuals, respectively) and larval (57.5% and 25.1% of all individuals, respectively) communities. The most abundant generalist species was nonnative invasive Harmonia axyridis (adults – 5.6%, larvae – 6.8% of all individuals). Adults and larvae of ladybirds were more abundant on solitary trees than on trees growing in groups. Our results confirmed that blue spruce hosts rich ladybird communities and provides them shelter and food resources.

Distribution and composition of Decapod larvae assemblages on the Berlengas archipelago and Peniche coast (western coast of Portugal)

For the first time, the decapod larval community in the Berlenga and coastal Peniche region have been investigated in detail, from a short-term time series (2015 – 2020). Sampling was conducted in two locations, at Berlengas archipelago, and near the coast, at Peniche. The communities found at both stations were revealed to be 80% different in terms of species composition, but species of Brachyura, Caridea, and Anomura were the most abundant in both locations. A marked seasonality, with abundance peaks during summer and autumn, was found for the assemblages near the coast, but absent in the assemblages of the Berlenga region. This suggests that factors other than the environmental variables examined in this study may play a crucial role in shaping the assemblages more offshore. Water temperature, upwelling index, salinity, and chlorophyll-a were the main factors dictating species abundance, especially at Peniche. This emphasizes the significant role of the Iberian upwelling productivity, which in turn influences decapod communities. Also, the progressive warming of coastal water will most likely have a negative impact on the decapod meroplanktonic life forms, with further consequences on recruitment and adult life stages.

Spatial structuring in early life stage fish diversity in the Scotia Sea region of the Southern Ocean

AbstractThe fish community of the Scotia Sea is diverse and plays key roles in Antarctic food webs and biogeochemical cycling. However, knowledge of the spatial and community structure of their early life stages is limited, particularly in the region surrounding the South Orkney Islands. Here we examine the structure of the early life stage fish community in the epipelagic using data from a basin-scale survey conducted in early 2019, which sampled the top 200 m of the water column. 347 early life stage fish from 19 genera were caught in 58 hauls. A third of all specimens belonged to the genus Notolepis and the nine most common genera comprised over 90% of specimens. Cluster analysis revealed five distinct groupings, the most common were a group dominated by pelagic and shelf slope genera (Notolepis, Muraenolepis and Electrona) found mainly in oceanic waters (depth ≥ 1000 m), and a group dominated by species with demersal or benthopelagic adults (Chionodraco, Chaenocephalus and Nototheniops) found mainly in shelf waters. Bottom depth was the main environmental determinant of community structure, separating the diverse on-shelf assemblage at the South Orkneys from the less species-rich community of widespread oceanic taxa. Our results indicate the highest diversities of early life stages of endemic fish occur on the shelf and near-shelf areas. Dedicated monitoring is recommended to understand the seasonal differences in larval community assemblages and the implications of early life stages fish bycatch within the krill fishery.

Interannual Variation of Ichthyoplankton Community Structure in the Yellow River Estuary, China

To understand the community structure dynamics of fish eggs and larvae in the Yellow River estuary, four trawl surveys were annually conducted between 2011 and 2014, including at 13 stations in 2011 and 18 stations between 2012 and 2014. A total of 2540 eggs and 143 larvae were collected during the four surveys, comprising 25 species, 8 orders, 16 families, and 20 genera. During the survey period, species numbers of eggs first decreased and then increased, while abundances first increased and then decreased. Larval species numbers exhibited the same trends as for eggs, while larval abundances fluctuated across the four years of the study. The primary species represented by the eggs were Konosirus punctatus, Sillago sihama, and Cynoglossus joyeri, while the larval species primarily comprised Amblychaeturichthys hexanema, Chaeturichthys stigmatias, and Engraulis japonicus. Cluster analysis of species compositions for eggs and larvae revealed the presence of four groups, wherein groups 1–3 comprised communities from 12, 3, and 2 stations, respectively, that were primarily distributed in the eastern part of the estuary. In contrast, group four only comprised communities from one station at the western part of the estuary near Bohai Bay. All biodiversity indices were lowest in 2012 and biodiversity of fish egg and larval communities were most correlated with the water depth among the parameters that were measured. Overall, interannual variation in the distribution and diversity of fish egg and larval communities in the Yellow River estuary reflected the responses of fish to environmental variability.

Mulching time of forest meadows influences insect diversity

Abstract The diversity in meadows is affected by numerous aspects, such as the amount and type of fertilisation and the timing and frequency of cutting. The effects of mowing on the diversity of plants and insects have been studied in detail. However, the effect of mulching (vegetation is cut, shredded, and left in place, instead of being removed) on insects in small forest meadows has received limited scrutiny to date. In this study, we examined how different mulching times influenced insect diversity of forest meadows. We sampled insect larvae and observed flower‐visiting insects at 24 sites in the Northern Black Forest in south‐west Germany. We applied four treatments with six replicates each: (i) mulching in June, (ii) mulching in September, (iii) mulching in June and September, and (iv) no mulching as a control. The overall larval community was dominated by Symphyta (45%, Hymenoptera) and Lepidoptera (44%). The flower‐visiting insect community was dominated by Syrphidae (80%, Diptera). The insect larvae were negatively influenced by all mulching treatments. The abundance and species richness of flower visitors was reduced by mulching in June only and by mulching in both June and September. Summary: Given that meadow management is required for conserving grassland diversity our results indicate that for insect larvae other mulching methods, than those we tested, such as mulching with an arthropod‐friendly mulching machine, strip‐mulching, or delayed mulching may help this crucial stage of insect development. For insect flower visitors mulching in September is beneficial.

Neritic larval fish assemblages across the Texas shelf in the northwestern Gulf of Mexico following Hurricane Harvey

AbstractFall is an important time of year for fish recruitment in the Gulf of Mexico, with many commercially and recreationally important species spawning during this period. Changes in temperature and salinity regimes through seasonally abnormal freshwater input may change spawning patterns and displace larvae. Such an event occurred off the coast of Galveston Bay, Texas, when a freshwater flood plume formed from unprecedented rainfall related to Hurricane Harvey at the end of August 2017. This study investigated the effects of a large‐scale flood plume on larval fish assemblages, collected at nearshore and shelf zones 1 and 2 months after Hurricane Harvey. Samples from 2017 were compared to historical datasets collected by NOAA Fisheries in September (2000–2004 and 2006–2016) and October (2000–2012). Evidence of lowered water temperature and salinity was found in both September and October 2017. Larval community composition changed along cross‐shelf gradients and with increasing distance from shore. We also found evidence of 2017 assemblages differing from historical data, with the September 2017 assemblage more closely resembling those from October historical samples. Observed differences in 2017 assemblages were most likely explained by an earlier onset in fall sciaenid spawning, suggesting that decreases in water temperature occurring during hurricanes have the potential to alter fish spawning patterns.

Within-host and external environments differentially shape β-diversity across parasite life stages.

Uncovering drivers of community assembly is a key aspect of learning how biological communities function. Drivers of community similarity can be especially useful in this task as they affect assemblage-level changes that lead to differences in species diversity between habitats. Concepts of β-diversity originally developed for use in free-living communities have been widely applied to parasite communities to gain insight into how infection risk changes with local conditions by comparing parasite communities across abiotic and biotic gradients. Factors shaping β-diversity in communities of immature parasites, such as larvae, are largely unknown. This is a key knowledge gap as larvae are frequently the infective life-stage and understanding variation in these larval communities is thus key for disease prevention. Our goal was to uncover links between β-diversity of parasite communities at different life stages; therefore, we used gastrointestinal nematodes infecting African buffalo in Kruger National Park, South Africa, to investigate within-host and extra-host drivers of adult and larval parasite community similarity. We employed a cross-sectional approach using PERMANOVA that examined each worm community at a single time point to assess independent drivers of β-diversity in larvae and adults as well as a longitudinal approach with path analysis where adult and larval communities from the same host were compared to better link drivers of β-diversity between these two life stages. Using the cross-sectional approach, we generally found that intrinsic, within-host traits had significant effects on β-diversity of adult nematode communities, while extrinsic, extra-host variables had significant effects on β-diversity of larval nematode communities. However, the longitudinal approach provided evidence that intrinsic, within-host factors affected the larval community indirectly via the adult community. Our results provide key data for the comparison of community-level processes where adult and immature stages inhabit vastly different habitats (i.e. within-host vs. abiotic environment). In the context of parasitism, this helps elucidate host infection risk via larval stages and the drivers that shape persistence of adult parasite assemblages, both of which are useful for predicting and preventing infectious disease.

Summer decapod crustacean larval communities along the eastern Spanish Mediterranean coast.

Decapod crustaceans are a diverse group englobing several species of commercial and ecological interest. In the Mediterranean Sea, decapod crustacean fisheries are among the most profitable, although in many cases their early life stages are poorly known. In this study, we tackle the composition and diversity patterns of the decapod larval communities along the eastern Spanish Mediterranean coast. Zooplankton sampling was carried out in surface waters at 101 stations from July 20th to August 31st 2016, over bottom depths between 90 and 1840 m. All shrimp larvae were identified to the lowest possible taxonomical level, and larvae from Anomura, Achelata and Brachyura were left at infraorder level. No larvae of Astacidea or Polychelida were found. The total zooplankton volume was estimated. A total of 20,022 decapod crustacean larvae were identified, focusing on shrimp taxa (suborder Dendrobranchiata and infraorder Caridea). Both zooplankton volume and decapod larval density values were higher in the northern part of the studied area, cut by deep submarine canyons. After assessing the diversity parameters of the decapod larval community, we present the summer mesoscale larval distribution of several species of commercial interest such as the caramote prawn (Penaeus kerathurus) or the deep-water rose shrimp (Parapenaeus longirostris). The northern submarine canyons are dominated by the presence of Penaeoidea, being the deep-sea shrimp Aristeus antennatus the dominant species in the community in this area, while the Sergestoidea are more abundant in the southern zone. This is the largest-scale study on decapod larvae mesoscale distribution in the Mediterranean Sea.

Impacts of Lysinibacillus sphaericus on mosquito larval community composition and larval competition between Culex pipiens and Aedes albopictus

Effectiveness of mosquito larvicide active ingredients (AI), such as Lysinibacillus sphaericus, varies between species, yet little is known regarding how differential effectiveness manifests in larval communities in applied settings. To examine how differential effectiveness of L. sphaericus influences larval community dynamics, we performed two experiments. We performed a field experiment in which containers were seeded with a standardized nutrient treatment, mosquitoes colonized the containers, and then containers received one of three L. sphaericus applications. We then performed competition assays between Culex pipiens and Aedes albopictus in low nutrient environments using multiple interspecific ratios and the presence/absence of a low dose of L. sphaericus. Field results demonstrated elimination of Culex spp. from treated containers while container breeding Aedes spp. proliferated across all treatments. Lysinibacillus sphaericus did not influence competition between Cx. pipiens and Ae. albopictus, and the L. sphaericus application eliminated Cx. pipiens in all treatment replicates while survival of Ae. albopictus was similar between treated and untreated containers across interspecific ratios. Lysinibacillus sphaericus is an effective AI for control of Culex spp. However, different AIs should be utilized in habitats containing non-Culex genera while a mix of AIs should be utilized where coexistence of multiple genera is expected or confirmed.

Fine scale environmental variability and physiological tolerance influence invertebrate larval communities from a human-impacted mangrove in Hong Kong

Macroinvertebrates that rely on a supply of planktonic larvae for recruitment play a significant role in maintaining productivity in mangrove ecosystems. Thus, identifying the spatial distribution and physiological limitations of invertebrate larval communities within mangroves is important for targeted conservation efforts to maintain population persistence amid the threat of climate change. Here, the role of spatial, lunar, and environmental factors in structuring invertebrate larval communities in Ting Kok, the second largest mangrove forest in Hong Kong, was examined. Results indicate that, spatially, invertebrate larval communities were influenced by environmental filtering, habitat type, and the lunar tidal cycle. This indicates the fundamental role of habitat heterogeneity and connectivity for the transport, distribution, and development of crustacean larvae. Larvae of key sesarmids exhibited metabolic depression at water temperatures forecasted to be regularly experienced by the year 2050, according to current climate projections. The impacts of climate change, coupled with habitat destruction and degradation of hydrological connectivity, make larval communities increasingly vulnerable to mass-mortality and displacement. This places ecosystem productivity and functionality at risk through cascading negative effects of recruitment limitation. Further focus on this subject will help disentangle the effects of process rates and scales of transport that underlie community assemblages in mangrove systems. Furthermore, identifying physiological bottlenecks of key taxa and habitat provisioning that enhance larval survival will be helpful to prioritize strategies for conservation management in dynamic intertidal settings.

Diet of Bullfrog Tadpoles Lithobates catesbeianus, Shaw 1802, an Invasive Species from Monte Desert

The competitive effects among tadpoles make the bullfrog a possible agent of native amphibian population declines at its introduction sites. Our aim was to analyze the dietary composition of an invasive population of Lithobates catesbeianus tadpoles and to evaluate the degree of dietary changes among activity months. We hypothesized that bullfrog tadpoles would exhibit temporal changes in diet, consistent with the variation of tadpole size and availability of resources. We collected 94 bullfrog tadpoles and identified 50 taxa in their digestive tracts. The items most frequently consumed were microalgae of the genera Navicula (frequency of occurrence [Fo] = 19) and Cymbella (Fo = 17). The trophic niche breadth was 8.13, which is considered moderate-high. The trophic habits of L. catesbeianus larvae changed seasonally, with the diets during October and December being numerically similar (Morisita's quantitative index = 0.86). The composition of the diet had a similarity of 63% (Jaccard's qualitative index) between August and October. The larvae of L. catesbeianus collected during the different months showed significant differences in their stages of development and body mass. On average, individuals were larger and more developed in the month of December, which was to be expected given that the abundance of prey items is greatest during the summer season. Our results show that L. catesbeianus tadpoles have a wide trophic niche with a diet that is not strongly selective; thus, the aquatic life-history stages play an important role in the structuring of invaded anuran larval communities.

Seasonal Occurrence of Caddisfly Larval Communities on a Coarse Substrate in the Upper Nan River, Northern Thailand

Abstract Caddisfly larvae are commonly found in the Nan River. Larvae were collected monthly from a cobble habitat for a period of two years to study the influence of seasonal changes on larval communities. A Surber sampler was placed in the cobble habitat in the riffle zone at four study sites along the upper Nan River. Field-collected larvae were identified at the family level in the laboratory. Physicochemical factors were measured in terms of water temperature, pH, turbidity, dissolved oxygen (DO) and biochemical oxygen demand (BOD5), as well as for concentrations of ammonia nitrogen (NH3-N), nitrate nitrogen (NO3-N) and orthophosphate (PO43-). Fifteen families of the caddisflies were found. The cool season was associated with the highest degree of density followed by the summer and rainy seasons. Hydropsychidae was the most common caddisfly present throughout the year. Hydroptilidae was common in the summer and cool seasons. Values of water temperature, pH, turbidity, DO, BOD5 and NO3-N among the three seasons were observed to be significantly different. According to the CCA analysis, water temperature, turbidity, BOD5, NO3-N and NH3-N factors had a positive relation to the density of Ecnomidae, Goeridae, Odontoceridae and Polycentropodidae. Remarkably, caddisfies in the families Hydropsychidae, Rhyacophilidae and Stenopsychidae were intolerant to variations in DO and pH values. The results of our study indicate that the physicochemical factors varied in conjunction with the different seasons, while communities and the degree of density of some caddisfly larvae were associated with variations of the physicochemical factors. Keywords: Trichoptera, Cobble, Environmental factors, Season

Effect of sainfoin (Onobrychis viciifolia) on cyathostomin eggs excretion, larval development, larval community structure and efficacy of ivermectin treatment in horses.

Alternative strategies to chemical anthelmintics are needed for the sustainable control of equine strongylids. Bioactive forages like sainfoin (Onobrychis viciifolia) could contribute to reducing drug use, with the first hints of in vitro activity against cyathostomin free-living stages observed in the past. We analysed the effect of a sainfoin-rich diet on cyathostomin population and the efficacy of oral ivermectin treatment. Two groups of 10 naturally infected horses were enrolled in a 78-day experimental trial. Following a 1-week adaptation period, they were either fed with dehydrated sainfoin pellets (70% of their diet dry matter) or with alfalfa pellets (control group) for 21-days. No difference was found between the average fecal egg counts (FECs) of the two groups, but a significantly lower increase in larval development rate was observed for the sainfoin group, at the end of the trial. Quantification of cyathostomin species abundances with an ITS-2-based metabarcoding approach revealed that the sainfoin diet did not affect the nemabiome structure compared to the control diet. Following oral ivermectin treatment of all horses on day 21, the drug concentration was lower in horses fed with sainfoin, and cyathostomin eggs reappeared earlier in that group. Our results demonstrated that short-term consumption of a sainfoin-rich diet does not decrease cyathostomin FEC but seems to slightly reduce larval development. Consumption of dehydrated sainfoin pellets also negatively affected ivermectin pharmacokinetics, underscoring the need to monitor horse feeding regimes when assessing ivermectin efficacy in the field.

Habitat Restoration Restores Underwater Soundscapes and Larval Recruitment

Habitat degradation alters many ecosystem processes, and the potential for the reestablishment of ecosystem function through restoration is an area of active research. Among marine systems, coastal habitats are particularly vulnerable to anthropogenic degradation and, in response, are the focus of marine ecological restoration. One of the crucial functions of structurally complex coastal habitats (e.g., saltmarshes, seagrass meadows, kelp forests, coral reefs) are as nurseries to coastal and offshore species, many of whose larvae utilize sound to locate suitable nursery habitat. However, the effect of habitat degradation and subsequent restoration on underwater soundscapes and their function as navigational cues for larvae is unexplored. We investigated these phenomena in sponge-dominated hardbottom habitat in the waters surrounding the middle Florida Keys (Florida, United States) that have been degraded in recent decades by massive sponge die-offs caused by harmful algal blooms. One of the consequences of sponge die-offs are dramatic changes in underwater sounds normally produced by sponge-associated animals. We tested whether soundscapes from healthy hardbottom habitat influenced larval recruitment, and then examined how hardbottom degradation and restoration with transplanted sponges affected underwater soundscapes and the recruitment of larval fishes and invertebrates. Larval assemblages recruiting to healthy areas were significantly different than those assemblages recruiting to either degraded or restored hardbottom areas. Fewer larvae recruited to degraded and restored areas compared to healthy hardbottom, particularly during the full moon. Experimental playback of healthy hardbottom soundscapes on degraded sites did not promote larval community differences although some individual species responded to the playback of healthy habitat soundscapes. These results indicate that habitat-associated soundscapes have idiosyncratic effects on larval settlement, which is diminished by the degradation of nursery habitat but can be reestablished with appropriate habitat restoration.

Origin of marine invertebrate larvae on an Arctic inflow shelf

Many benthic invertebrate taxa possess planktonic early life stages which drift with water currents and contribute to dispersal of the species, sometimes reaching areas beyond the current ranges of the adults. Until recently, it had been difficult to identify planktonic larvae to species level due to lack of distinguishing features, preventing detection of expatriate species. Here, we used DNA metabarcoding of the COI gene to obtain species-level identification of early life stages of benthic invertebrates in zooplankton samples from the Barents Sea and around Svalbard, where, regionally, large volumes of warm Atlantic Water enter the Arctic from the south. We compared the larval community in the water column to the adult community on the seafloor to identify mismatches. In addition, we implemented particle tracking analysis to identify the possible areas of origin of larvae. Our results show that 30-45% of larval taxa—largely polychaetes and nudibranchs—were not local to the sampling area, though most were found nearby in the Barents Sea. In the particle tracking analysis, some larvae originating along the Norwegian coast were capable of reaching the northwest coast of Svalbard within 3 mo, but larvae found east of Svalbard had a more constrained possible area of origin which did not extend to the Norwegian coast. This study highlights largely regional-scale larval connectivity in the Barents Sea but demonstrates the potential for some long-lived larval taxa to travel to Svalbard and the Barents Sea from further south.

Black Soldier Fly Larvae Can Effectively Degrade Oxytetracycline Bacterial Residue by Means of the Gut Bacterial Community.

Antibiotic bacterial residue is a unique hazardous waste, and its safe and effective disposal has always been a concern of pharmaceutical enterprises. This report presents the effective treatment of hazardous waste—antibiotic bacterial residue—by black soldier fly larvae (larvae), oxytetracycline bacterial residue (OBR), and soya meal with mass ratios of 0:1 (soya), 1:20 (OBRlow), and 1:2 (OBRhigh), which were used as substrates for larval bioconversion. Degradation of OBR and oxytetracycline, the bacterial community, the incidence of antibiotic resistance genes (ARGs) and the bacterial function in the gut were examined. When the larvae were harvested, 70.8, 59.3, and 54.5% of the substrates had been consumed for soya, OBRlow and OBRhigh; 65.9 and 63.3% of the oxytetracycline was degraded effectively in OBRlow and OBRhigh, respectively. The larval bacterial communities were affected by OBR, abundant and various ARGs were discovered in the gut, and metabolism was the major predicted function of the gut. These findings show that OBR can be digested and converted by larvae with gut bacteria, and the larvae can be used as a bioremediation tool for the treatment of hazardous waste. Finally, the abundant ARGs in the gut deserve further attention and consideration in environmental health risk assessments.

Potential future climate-induced shifts in marine fish larvae and harvested fish communities in the subtropical southwestern Atlantic Ocean

The continental shelf in the southwestern Atlantic Ocean is among the six richest marine regions for biodiversity in the Southern Hemisphere, and its subtropical region is one of the fastest-warming hotspots. Thus, climate change could profoundly affect future species distributions. We investigated future climate-induced changes in fish larvae and harvested fish taxa in the subtropical southwestern Atlantic Ocean using a community-based modelling technique (gradient forest). This approach integrates information on multiple species rather than treating each species individually, as is typical in many species distribution approaches. We addressed two primary questions: how might climate change affect fish larval communities, and will communities of harvested fish (juveniles and adults) taxa respond similarly. Using two climate change scenarios (moderate RCP 4.5 and ‘business as usual’ 8.5), we found that fish larvae and harvested taxa are influenced differently by environmental variables, with differences in both the level and shape of the response to environmental drivers. Chlorophyll a and sea surface temperature were the most important predictors for fish larvae communities, while depth and sea surface salinity best predicted the harvested community. However, both communities are expected to move southwards in response to climate change, with greater changes in community composition predicted in the southern portion of the study area for both fish larvae and harvested taxa. To our knowledge, this is the first study to investigate the effect of future climate change on a suite of taxa of fish larvae and adults. We also suggest that modelling the integrated response of a suite of species to environmental predictors using community-modelling approaches such as gradient forest could provide robust projections and novel insights into community changes.

Formalin-Fixed Fish Larvae Could Be Effectively Identified by DNA Barcodes: A Case Study on Thousands of Specimens in South China Sea

Delimiting ichthyoplankton is fundamental work for monitoring the recruitment process and identifying the spawning and nursing grounds of fishes. Nevertheless, it is extremely difficult to identify the fish during the early stages at the species level based on morphological characters because of the paucity of diagnostic features. In this study, we investigated the fish larval community through large-scale ecosystemic sampling in South China Sea (SCS) during 2013 and 2017 using DNA barcodes. To maintain the morphologies of fish larvae, we preserved the larvae in formalin and developed a technique to recover their DNA. Among the 3,500 chosen larvae, we successfully extracted DNA from 2,787 larval samples and obtained 1,006 high-quality sequences. Blast searches showed that 408 larvae (i.e., 40.5%) could be unambiguously identified to species, 413 larvae (i.e., 41.1%) were ambiguously species delimitation, and 185 larvae (i.e., 18.4%) showed a low match similarity with target sequences. A total of 101 species were identified, among which 38 and 33 species corresponded to demersal and reef-associated species, whereas the remaining 30 species corresponded to benthopelagic, pelagic-oceanic, bathypelagic, and pelagic-neritic species. High-quality larval photographs of the 101 diagnosed species showed intact morphological characters and thus provided a reference for identifying fish species during the early stages based on morphological characters. Our study highlighted the possibility of recovering and amplifying DNA from formalin-fixed samples and provided new insight into the fish larval community in the SCS.

Ecological scaling in mangroves: The role of microhabitats for the distribution of larval assemblages

Mangroves are regarded as important spawning and settlement grounds as well as nurseries for larvae and juvenile fishes and invertebrates due to the sheltered nature of these ecosystems. The present study examined the spatial and temporal distribution of fish and invertebrate larvae, simultaneously among several microhabitats, within two South African mangrove forests. Results indicate that despite temperature and salinity homogeneity across microhabitats, spatio-temporal differences occurred in both fish and invertebrate larval assemblages. The distinct larval assemblages were driven by the site-specific predisposition of taxa to occur more abundantly in one or more specific microhabitats, while temperature, salinity and tidal phase temporally structured both invertebrate and fish larval communities. The larvae of estuarine dependent marine fish occurred in mangrove microhabitats, suggesting they use structural mangrove patchiness as corridors or temporary nurseries before settling in situ, into their juvenile habitat. This study steers that the proposed nursery function or early stage role that mangroves play is driven by the structural uniqueness of mangrove microhabitats thus ensuring localised ecological linkages and functionality of these critical coastal environments.