Habitat conditions in streams influence Odonata larval assemblages in the eastern Amazon

The growth of agricultural and mining activities in the Amazon has impacted land-use and caused significant changes in the local environmental conditions of streams. In the face of these changes, our study aimed at assessing how environmental changes affect Odonata larval assemblages in streams in the eastern Amazon. We hypothesized that habitat conditions in streams are strong predictors of Odonata larval assemblages. We sampled 30 headwater streams (1st through 3rd order) in the eastern Amazon. We corroborated our hypothesis that regional- and local-scale environmental changes are important predictors of the Odonata larval assemblage structure. These results indicate that environmental conditions within the stream channel are important to maintain Odonata larval assemblages, as they provide important resources for larval development. For new studies, we recommend the assessment of temporal dynamics to evaluate whether these patterns are stable across time. Finally, evaluating various environmental scales of the original impact is extremely relevant for preventing the deterioration of or recuperating aquatic assemblages in Amazonian streams, considering the ongoing rapid environmental changes and deforestation in the region. Here we demonstrate that in-stream environmental conditions are important to assemblage structure and this must be considered in environmental restoration plans.

Estuarine Infauna Within Incidentally Retained Sediment in Artificial Rockpools

Artificial coastal structures (ACSs) are primarily designed to provide services for human use, such as flood defence or shipping, and are generally poor for marine biodiversity. Consequently, there has been significant research effort to enhance these hard structures to increase biodiversity and habitat availability via eco-engineering. On seawalls and breakwaters, this has included the creation of habitats for benthic species found on natural rocky shores, including the provision of cracks, crevices and water retaining features, such as artificial rockpools. When sediment retention in these features has occurred, it has often been deemed detrimental to the overarching aim of the intervention. Yet, it is soft sediment habitat that is impacted the most through coastal construction. As ecological enhancement of a flood defence scheme, nine concrete retrofit rockpools were installed at three different tidal elevations between mean high water neap tide and mean tide level on steel sheet piling on the Arun Estuary in Littlehampton Harbour, United Kingdom, which naturally filled with mud 1 year after installation. To explore how analogous the faunal assemblages and sediment profile of rockpool mud were to two local mudflats, core samples were taken and analysed for species richness, abundance, biomass, assemblage structure, median grain size, and organic matter content. More benthic species were observed in the artificial rockpool than in the local mudflats. Although the rockpools were placed at higher tidal levels than the lower shore mudflat, their assemblage structure and species richness were more similar to the lower shore mudflat at the base of the sheet piling than the upper shore mudflat. This study demonstrates that retained sediment within eco-engineered features on hard ACSs can create habitat for benthic assemblages. Providing sediment-retentive features on ACSs has the potential to provide a novel eco-engineering option that may be appropriate for some heavily modified waterbodies on sheltered, depositional coasts.

Spring Ichthyoplankton Assemblage Structure in the Yangtze Estuary Under Environmental Factors

Estuaries, where fresh and salty water converge, provide abundant nutrients for ichthyoplankton. Ichthyoplankton, including fish eggs, larvae, and juveniles, are important fishery recruitment resources. The Yangtze Estuary and its adjacent waters comprise a typical large-scale estuary and supply many important fish spawning, feeding, and breeding areas. In this study, 1,291 ichthyoplankton individuals were collected in the Yangtze Estuary in spring, from 2013 to 2020. The aims of the study were to provide detailed information on characteristics of the ichthyoplankton assemblage, explore interannual variation, and evaluate the effects of environmental variables on the temporal variation in assemblage structure. Twenty-six species in seventeen families were identified. The dominant species were Coilia mystus, Chelidonichthys spinosus, Engraulis japonicus, Hypoatherina valenciennei, Larimichthys polyactis, Salanx ariakensis, Stolephorus commersonnii, and Trachidermus fasciatus. The ichthyoplankton assemblage changed significantly over time, and Chelidonichthys spinosus became one of the dominant species. Canonical correspondence analysis showed that temperature and chlorophyll a were the key factors affecting the assemblage structure in the Yangtze Estuary in spring.

Antarctic Special Protected Area 161 as a Reference to Assess the Effects of Anthropogenic and Natural Impacts on Meiobenthic Assemblages

The Antarctic region is usually considered a pristine area. Nevertheless, regional warming effects and increasing human activities, including the presence of several research stations, are inducing considerable environmental changes that may affect the ecosystem’s functions. Therefore, during the XXXIII Antarctic expedition, we carried out an investigation in Terra Nova bay (Ross Sea), close to the Antarctic Specially Protected Area (ASPA) n.161. In particular, we compared the effects of two different types of impacts on the meiobenthic assemblages: anthropogenic impact (AI), associated with the activity of Mario Zucchelli Research Station (MZS), and natural impact (NI) attributable to a large colony of Adélie penguins (Pygoscelis adeliae) in Adelie Cove. For each impacted site, a respective control site and two sampling depths (20 and 50 m) were selected. Several environmental variables (pH, dissolved oxygen, major and minor ions, heavy metals, organic load, and sediment grain size) were measured and analysed, to allow a comprehensive characterization of the sampling areas. According to the criteria defined by Unites States Environmental Protection Agency (US EPA 2009), heavy metal concentrations did not reveal critical conditions. However, both the MZS (AI20) and penguin colony (NI20) sites showed higher heavy metal concentrations, the former due to human activities related to the Italian research station, with the latter caused by the penguins excrements. Meiobenthic richness and abundance values suggested that the worst ecological condition was consistently related to the Adélie penguins colony. Furthermore, the higher contribution of r-strategists corroborates the hypothesis that the chronic impact of the penguin colonies may have stronger effects on the meiobenthos than the human activities at the MZS. Food is not limited in shallow Antarctic bottoms, and microscale differences in primary and secondary production processes can likely explain the greater spatial heterogeneity, highlighted both by the univariate and multivariate attributes of meiobenthic assemblage (i.e., richness, diversity, abundance, whole structure assemblage, and rare taxa) at the deeper stations. As reported in other geographical regions, the assemblage structure of rare meiobenthic taxa is confirmed to be more susceptible to environmental variations, rather than the whole assemblage structure.

The Ecological Impacts of Mining at Seafloor Massive Sulfide Deposits on Megafaunal Assemblage Structure and Population Connectivity

<p>Deep-sea mining is rapidly becoming a reality, yet there are considerable gaps in our knowledge of the seabed assemblages that could be affected by mining activities. Seafloor Massive Sulfide (SMS) mining is expected to remove nearly all organisms in the immediate area and alter the remaining habitat, so that mitigation strategies for SMS mining will most likely need to include the establishment of protected areas to preserve the biodiversity that is lost at mine sites. Prospecting licences have been issued previously for SMS deposits within the New Zealand Exclusive Economic Zone (EEZ), however little is known about the seabed assemblages potentially at risk from SMS mining, particularly with respect to their structure (at multiple spatial scales) and the connectivity of assemblages at different sites. Designing studies to provide this information can be aided by turning to terrestrial, freshwater and shallow marine systems, where the fields of ecological theory, environmental management and conservation theory are better developed (Chapter 1). Prior to detailed investigations into the assemblage structure and population connectivity of New Zealand SMS deposits, it is essential to understand the global context of SMS mining. This was undertaken through an extensive literature review of SMS deposits, including their geology, seafloor communities, impacts from mining, international and national regulation, and environmental management (Chapter 2). In order to investigate the large-scale spatial distribution and structure of seafloor assemblages at SMS deposits, three New Zealand seamounts previously licenced for the prospecting phase of SMS mining were surveyed. Video footage from a towed camera was analysed to identify and characterise assemblages, and their association with environmental variation was investigated. Analysis of 249 video samples (each 250 m in length) distributed amongst the three seamounts indicated that SMS deposits support unique assemblages and that there were strong links between assemblage structure and environmental variation at a range of spatial scales. There was also a complex distribution of assemblages amongst the seamounts, suggesting a network of protected areas would be the most effective method for spatial management. Such networks should include sites that support the unique assemblages found in association with SMS deposits (Chapter 3). The fine-scale distribution and structure of assemblages at SMS deposits was investigated by using data from a single SMS deposit, Proteus 1, and comparing it to a Reference Site selected to have similar size and seabed characteristics to the deposit. Video footage from a Remotely Operated Vehicle (ROV) was used to identify and characterise assemblages, and their association with environmental conditions. Analysis of 153 video samples (each 15 m in length) confirmed the existence of assemblages unique to SMS deposits, and indicated that environmental characteristics specific to the deposit are responsible for the observed patterns of faunal distribution. Although five assemblages were shared between Proteus 1 and the Reference Site, six assemblages were unique to Proteus 1. This suggested that the proposed Reference Site would be inadequate on its own in terms of protecting the biological diversity present at the mine site but could contribute to a network of protected areas (Chapter 4). The issue of connectivity was addressed by examining the genetic connectivity of populations of the endemic hydrothermal vent mussel, Gigantidas gladius. Universal markers, archived material and off-the-shelf DNA extraction kits were used to investigate a cost effective approach. The assessment utilised variation in 586 base pairs of the mitochondrial cytochrome oxidase I subunit (COI) from 150 individuals in seven populations of G. gladius. Small sample sizes limited the recommendations that could be made for environmental management; however interpretation of the available sequences indicated panmixia with limited genetic structure and high connectivity amongst populations. Central Kermadec Volcanic Arc populations had particularly high haplotypic diversity and migrant exchange, suggesting they could be important for maintaining regional genetic connectivity and would merit inclusion in seabed protection measures (Chapter 5). Establishing protected areas for biodiversity needs to utilise all of the available information. The integrated findings of this thesis highlight the need for a network of protected seabed areas along the Kermadec Volcanic Arc to help mitigate the impacts of any future SMS mining activities. These networks should be highly connected (as determined by genetic connectivity) and include both active and inactive SMS areas to conserve 1) the endemic vent fauna in active areas and 2) the unique assemblages found in both environments (Chapter 6).</p>

The Ecological Impacts of Mining at Seafloor Massive Sulfide Deposits on Megafaunal Assemblage Structure and Population Connectivity

<p>Deep-sea mining is rapidly becoming a reality, yet there are considerable gaps in our knowledge of the seabed assemblages that could be affected by mining activities. Seafloor Massive Sulfide (SMS) mining is expected to remove nearly all organisms in the immediate area and alter the remaining habitat, so that mitigation strategies for SMS mining will most likely need to include the establishment of protected areas to preserve the biodiversity that is lost at mine sites. Prospecting licences have been issued previously for SMS deposits within the New Zealand Exclusive Economic Zone (EEZ), however little is known about the seabed assemblages potentially at risk from SMS mining, particularly with respect to their structure (at multiple spatial scales) and the connectivity of assemblages at different sites. Designing studies to provide this information can be aided by turning to terrestrial, freshwater and shallow marine systems, where the fields of ecological theory, environmental management and conservation theory are better developed (Chapter 1). Prior to detailed investigations into the assemblage structure and population connectivity of New Zealand SMS deposits, it is essential to understand the global context of SMS mining. This was undertaken through an extensive literature review of SMS deposits, including their geology, seafloor communities, impacts from mining, international and national regulation, and environmental management (Chapter 2). In order to investigate the large-scale spatial distribution and structure of seafloor assemblages at SMS deposits, three New Zealand seamounts previously licenced for the prospecting phase of SMS mining were surveyed. Video footage from a towed camera was analysed to identify and characterise assemblages, and their association with environmental variation was investigated. Analysis of 249 video samples (each 250 m in length) distributed amongst the three seamounts indicated that SMS deposits support unique assemblages and that there were strong links between assemblage structure and environmental variation at a range of spatial scales. There was also a complex distribution of assemblages amongst the seamounts, suggesting a network of protected areas would be the most effective method for spatial management. Such networks should include sites that support the unique assemblages found in association with SMS deposits (Chapter 3). The fine-scale distribution and structure of assemblages at SMS deposits was investigated by using data from a single SMS deposit, Proteus 1, and comparing it to a Reference Site selected to have similar size and seabed characteristics to the deposit. Video footage from a Remotely Operated Vehicle (ROV) was used to identify and characterise assemblages, and their association with environmental conditions. Analysis of 153 video samples (each 15 m in length) confirmed the existence of assemblages unique to SMS deposits, and indicated that environmental characteristics specific to the deposit are responsible for the observed patterns of faunal distribution. Although five assemblages were shared between Proteus 1 and the Reference Site, six assemblages were unique to Proteus 1. This suggested that the proposed Reference Site would be inadequate on its own in terms of protecting the biological diversity present at the mine site but could contribute to a network of protected areas (Chapter 4). The issue of connectivity was addressed by examining the genetic connectivity of populations of the endemic hydrothermal vent mussel, Gigantidas gladius. Universal markers, archived material and off-the-shelf DNA extraction kits were used to investigate a cost effective approach. The assessment utilised variation in 586 base pairs of the mitochondrial cytochrome oxidase I subunit (COI) from 150 individuals in seven populations of G. gladius. Small sample sizes limited the recommendations that could be made for environmental management; however interpretation of the available sequences indicated panmixia with limited genetic structure and high connectivity amongst populations. Central Kermadec Volcanic Arc populations had particularly high haplotypic diversity and migrant exchange, suggesting they could be important for maintaining regional genetic connectivity and would merit inclusion in seabed protection measures (Chapter 5). Establishing protected areas for biodiversity needs to utilise all of the available information. The integrated findings of this thesis highlight the need for a network of protected seabed areas along the Kermadec Volcanic Arc to help mitigate the impacts of any future SMS mining activities. These networks should be highly connected (as determined by genetic connectivity) and include both active and inactive SMS areas to conserve 1) the endemic vent fauna in active areas and 2) the unique assemblages found in both environments (Chapter 6).</p>

Vascular epiphyte assemblage structure and distribution patterns in the south-temperate zone

<p>Vascular epiphytes, which are specialised to spend their entire life cycle within trees, are significant contributors to local ecosystem services. However, our current understanding of epiphyte distributions, co-occurrences, and general ecology lags far behind that of terrestrial plants. Furthermore, the majority of epiphyte research is undertaken in tropical forests, with comparatively few studies extending into temperate climates. As such, whether epiphytic plant assemblage structure varies geographically, or is influenced by area and isolation effects needs further scrutiny. In addition, how epiphytes are distributed in relation to host tree ontogeny and microclimates specific to south-temperate forests is poorly understood. Here, I attempt to bridge this gap by researching epiphyte distributions and assemblage structure in New Zealand, southern Chile, and Australia. In the first biogeographic study of epiphyte-host interactions, I determined if epiphyte-host network structure (i.e. nestedness, species co-occurrences, species specialisation) varied among New Zealand and Chilean temperate forests (Chapter 2). At the forest stand level, network structure was consistent with stochastic structuring, which suggests that dispersal and disturbances are important drivers of epiphyte distributions at a biogeographic scale. However, deterministic structure was observed in New Zealand networks with regards to nestedness (i.e. when specialists interact with generalists), which suggests that positive species interactions influence epiphyte distributions at a within-tree scale. Second, I determined whether the composition of plant communities residing in epiphytic birds’ nest ferns (Asplenium goudeyi) on Lord Howe Island, Australia, are influenced by fern size, isolation from a major propagule source and resident plant community richness (Chapter 3). Results suggest that plant communities are structured by dispersal. For one, there was a significant isolation effect on resident plant community richness. Additionally, wind-dispersed taxa were well represented in isolated ferns, while animal-dispersed taxa and taxa with no specific dispersal strategies were absent. This is the first study to test the combined effects of area, isolation and resident plant richness on epiphytic plant assemblage structure. Third, using Darwin’s geological theory of island ontogeny as a theoretical construct, I explored changes in epiphyte species richness throughout tree ontogeny (Chapter 4). Theoretical frameworks have helped bridge the gap between our understanding of vascular epiphytes and terrestrial plants, however, none have been implemented to guide investigations on epiphyte assemblage development. Based on the general features of island ontogeny, I found three stages of epiphyte assemblage development: (i) an initial stage where host trees are devoid of epiphytes, (ii) a second stage where trees acquire epiphytes into maturity, and (iii) a hypothetical stage where epiphyte assemblages follow a period of species decline following host tree mortality. In addition to these results, I found interspecific variation in the ontogenetic stage at which host trees become favourable for epiphyte establishment and the rate at which epiphyte assemblages develop. Lastly, I explored the systematic distribution of epiphytes and mistletoes in relation to microclimate gradients around the trunks of trees (Chapter 5). In addition, I tested the physiological responses of epiphytes and mistletoes to reductions in their most limiting resources to determine if the responses were consistent with their distribution patterns. The radial distributions of epiphytes and mistletoes were highly directional, and paralleled gradients of humidity, light and water. Additionally, the photochemical efficiency of epiphytes and CO₂ assimilation in mistletoe leaves decreased in plants growing in environments with lower water and light availability, respectively. However, mistletoe leaves still assimilated CO₂ in lower light conditions, which suggests a high plasticity of mistletoes to growing in a canopy environment. Despite over 120 years of recognising the importance of vertical microclimates on epiphyte distributions, this is the first systematic study of epiphytic plant distributions in relation to microclimate gradients around the trunks of trees. This thesis has increased our understanding of epiphytic plant assemblage structure, and how it is influenced by host tree species, isolation, area and resident plant species richness. In addition, this thesis has increased our understanding of the effect of host tree ontogeny and microclimate on epiphyte distribution patterns. Together, these studies may be built upon more broadly to further elucidate drivers of epiphyte assembly and distribution patterns.</p>