Marine and Freshwater Research
Volume 68
Number 9 2017
Inclusion of a social perspective in conservation research in addition to the natural sciences can lead to a more holistic and far-reaching result. Yet, few studies cross borders to be truly multidisciplinary. This perspective addresses previous calls for collaborating authors to share their experiences and considers the existing limitations and ways forward to support multidisciplinary research in conservation science.
CO2 concentration in freshwater environments is rising, but is also poorly understood, particularly when compared to in marine environments. We sought to test predation success of a common freshwater fish in elevated CO2, and found that even very high concentrations of CO2 did not affect predation success. With little research having investigated biological and ecological outcomes of high CO2 in freshwater, our work suggests a difference in expectations from elevated CO2 marine biota and systems.
The biogeochemistry of surficial marine sediments is poorly known in Australia. The aim of the present study was to summarise a large suite of seabed biogeochemical ‘baseline’ data and to make inferences about the processes that govern the concentrations. The datasets have redressed some regional and global data gaps and led to improved knowledge about processes that support benthic diversity in Australia’s marine jurisdiction.
Bacteria with low (LNA) and high (HNA) nucleic acid content are widely distributed in aquatic environments. Their geographical distribution on a large river-catchment scale was investigated. The strong covariation of cytometric expressions between LNA and HNA indicated that they were intrinsically linked. The abundance and cytometric characteristics of LNA and HNA were regulated differently. The results suggest that they play different ecological roles in river ecosystems.
This study provides important limnological data collected in the semi-arid Eastern Cape Karoo region of South Africa before hydraulic fracturing impacts. It was found that depression wetlands and rivers had distinct physicochemical signatures, whereas dams exhibited variable characteristics that were similar to those of either rivers or depression wetlands. These data are important as baseline for long-term monitoring of freshwater ecosystems in the region.
A rapid assessment of paperbark (Melaleuca spp.) decline in permanent freshwater wetlands of the Djelk Indigenous Protected Area, northern Australia, was conducted by scientists and local Aboriginal Rangers. The decline was significantly correlated with poor water quality (high electrical conductivity, turbidity, ammonium), which, in turn, was correlated with feral buffalo activity, suggesting an indirect effect of buffalo on paperbark health.
Hydro-engineering constructions such as groynes change hydromorphology of rivers and affect their aquatic biota. Investigation of odonate fauna from the River Oder, Poland, revealed that groynes increased the abundances, species richness and diversity of dragonflies by creating the mosaics of heterogeneous habitats inhabited by species with particular preferences. The presence of groynes may be essential to the restoration or stabilisation of the populations of certain species and to renaturalisation processes in large rivers.
We evaluated the sensitivity of 12 ecological indicators that characterise fish abundance, body size and trophodynamics with respect to temporal scales. The study explicitly accounted for trophic interactions in the responsiveness and detectability of the indicators, by using a size-spectrum model. The results demonstrated the essential non-linear relationship between EIs and fishing pressures and highlighted potential misinterpretation of indicator temporal dynamics.
Water quality in Lake Roxen, Sweden, is improving, but an expected development towards larger predatory fish is missing. Cormorant diet, recovery of tagged fish, gill-nets surveys and commercial-fishery catches were used to describe the potential effects of cormorant predation. Results indicated that cormorants and fisheries may both be responsible for the lack of recovery. Cormorant predation keeps recruitment high, but the number of fish that reach large sizes remains low.
Microhabitat preferences of caddisfly species in four rivers in north-western Spain were analysed, namely, macrophytes, moss, pebbles and sand. Significant differences in the abundance of seven species (Drusus bolivari, Glossosoma privatum, Larcasia partita, Micrasema longulum, M. servatum, M. gr. moestum and Sericostoma sp.) were found among substrates, confirming that they have substrate preferences.
In many coastal tropical streams, omnivorous shrimp and aquatic insects cause the breakdown of leaf material that falls into the stream. To investigate the relationships between omnivorous shrimp, aquatic insects and leaf breakdown, we excluded either shrimp alone or shrimp and insects from leaf packs by creating electric fields. Leaves broke down fastest when shrimp, but not insects, were excluded, indicating that shrimp are potential predators of insects that are the principal processors of leaves in this stream ecosystem.
Sources of organic matter within the Río de la Plata estuary were investigated by stable isotopic analysis. Upper reaches were highly influenced by terrestrial and freshwater sources, lower reaches were mostly influenced by marine organic matter, and marsh habitats did not supply sediments into the estuary. El Niño events influenced the spatial dynamics of sources within the estuary.
Organisms such as stingrays may vary their habitat selection based on a variety of environmental factors, and their location can indirectly provide insight into the distribution of both their prey and their predators. The purpose of this study was to determine whether tidal stage and diel period affected the movements of Atlantic stingrays (Dasyatis sabina); and we found that they consistently used tidal currents to access their habitat, but only varied habitat selection with diel period in the winter. These movements may affect the probability of a stingray encountering predators, competitors and prey.
This study presents the first detailed information on movement patterns in Australian waters for the poorly known false killer whale (Pseudorca crassidens). We satellite tracked four individuals over ~3–4 months, in coastal waters of the Northern Territory, finding total dispersal distances of ~5000–8000 km over that period. Prior to this study, information deficiencies meant that this species was largely unconsidered in conservation planning and management in Australian coastal waters; the information obtained in this study will allow this deficiency to be remedied.
In this study the causes and rates of blacktip reef shark (Carcharhinus melanopterus) mortality during gill-net capture were assessed. The results demonstrated that juvenile blacktip reef sharks are more likely to die during capture than adults. If populations decrease in the future, fisheries regulations designed to conserve the species should focus on reducing juvenile encounters with gill-nets.
We hypothesised that Phormidium biofilms better use sediments as a nutrient resource than diatoms, and thus Phormidium proliferations would increase with forestry cover in the catchment affecting river ecosystem functioning. Cover of Phormidium increased with the proportion of forestry in the catchment, and river ecosystem metabolism increased with this abundance, suggesting that pine forestry promotes ecological changes along the New Zealand rivers.
Physical processes that determine the spatial distribution of Zostera seagrass in Port Phillip Bay, Australia, were investigated by examining the links between seagrass abundance and broadscale hydrodynamic (waves, currents), physical (light, depth, salinity and temperature) and catchment (nutrient and suspended sediment concentrations) processes. The present study found that the distribution of seagrass meadows is principally constrained by two physical thresholds, namely, wave height or exposure and light. The former excludes seagrasses from colonising wave-exposed coastlines, whereas the latter directly determines the depth profile of seagrasses through its influence on light availability.
This study used underwater cameras to examine how the width of fringing mangrove habitats affected the composition and use patterns of the fish assemblage using mangrove edge habitats in an urbanised estuary on the flooding tide. Both wide and narrow mangroves were found to be viable habitats for estuarine fish.
Jellyfish often carry other animals with them as they swim through coastal waters, yet ecological data on these relationships are scarce. The relationship between a large jellyfish and an associated isopod and anemone was studied over 2 years. The isopod was prevalent on the jellyfish nearly year round, whereas the anemone occurred less often and only between autumn and spring.