Terrestrial invertebrates of dry river beds are not simply subsets of riparian assemblages

Dry river beds are common worldwide and are rapidly increasing in extent due to the effects of water management and prolonged drought periods due to climate change. While attention has been given to the responses of aquatic invertebrates to drying rivers, few studies exist on the terrestrial invertebrates colonizing dry river beds. Dry river beds are physically harsh and they often differ substantially in substrate, topography, microclimate and inundation frequency from adjacent riparian zones. Given these differences, we predicted that dry river beds provide a unique habitat for terrestrial invertebrates, and that their assemblage composition differs from that in adjacent riparian zones. Dry river beds and riparian zones in Australia and Italy were sampled for terrestrial invertebrates with pitfall traps. Sites differed in substrate type, climate and flow regime. Dry river beds contained diverse invertebrate assemblages and their composition was consistently different from adjacent riparian zones, irrespective of substrate, climate or hydrology. Although some taxa were shared between dry river beds and riparian zones, 66 of 320 taxa occurred only in dry river beds. Differences were due to species turnover, rather than shifts in abundance, indicating that dry river bed assemblages are not simply subsets of riparian assemblages. Some spatial patterns in invertebrate assemblages were associated with environmental variables (irrespective of habitat type), but these associations were statistically weak. We suggest that dry river beds are unique habitats in their own right. We discuss potential human stressors and management issues regarding dry river beds and provide recommendations for future research.     

Atmospheric vapour and precipitation are not in isotopic equilibrium in a continental mountain environment

Isotopic exchange with atmospheric vapour can strongly influence the isotopic values of evaporating surface water bodies (e.g., lakes), influencing our understanding of hydrological processes across aquatic and terrestrial environments. Rather than measure the isotopic values of the atmosphere directly, it is much more common to estimate values by assuming equilibrium with local precipitation. This assumption may introduce large errors, thereby biasing hydrological inferences and understanding. The pattern and magnitude of this error has been quantified only in a few circumstances. We compared observations of vapour and precipitation isotope values over a four-year record collected in a montane environment in the central Rocky Mountains of North America. We further investigated factors and conditions promoting disequilibrium. Scenario comparisons assessed the impact of theoretical and methodological elements on the accuracy of the equilibrium assumption. We found that the equilibrium assumption was not well supported by direct and continuous observations of vapour isotopes using tower-based laser isotope spectroscopy, particularly during the summer months. Across all scenarios, errors associated with the equilibrium assumption were high, credibly ranging from 14 to 154 ‰ for δ²H and 1.5 to 16.3 ‰ for δ¹⁸O. Environmental covariates (e.g., vapour pressure deficit, air pressure) helped explain some of the apparent disequilibrium. Although the equilibrium assumption for estimating atmospheric vapour isotope values may not be applicable in a continental montane environment, our findings highlight opportunities for using direct vapour isotope measurements to better understand vapour sources, air mass mixing, and phase changes over complex mountainous terrain, which in turn may better constrain regional- to global-scale hydrological process estimates, such as evapotranspiration rates and the water budgets of mountain lakes.     

Epiphyte loads on seagrasses and microphytobenthos abundance are not reliable indicators of nutrient availability in oligotrophic coastal ecosystems

Despite marked gradients in nutrient availability that control the abundance and species composition of seagrasses in south Florida, and the importance of nutrient availability in controlling abundance and composition of epiphytes on seagrasses in other locations, we did not find that epiphyte load on the dominant seagrass, Thalassia testudinum, or that the relative contribution of algal epiphytes to the epiphyte community, was positively correlated with nutrient availability in the water column or the sediment in oligotrophic seagrass beds. Further, the abundance of microphytobenthos, as indicated by Chlorophyll-a concentration in the sediments, was not directly correlated with concentrations of nutrients in the sediments. Our results suggest that epiphyte and microphytobenthos abundance are not unambiguous indicators of nutrient availability in relatively pristine seagrass environments, and therefore would make poor candidates for indicators of the status and trends of seagrass ecosystems in relatively low-nutrient environments like the Florida Keys.     

Legal protection is not enough: Posidoniaoceanica meadows in marine protected areas are not healthier than those in unprotected areas of the northwest Mediterranean Sea

Using the Conservation Index, which measures the proportional amount of dead matte relative to live Posidonia oceanica, we assessed the health of 15 P. oceanica meadows at a regional scale along the coast of Liguria (NW Mediterranean). These areas were characterized by different degrees of anthropization, from highly urbanized sites to marine protected areas. Two different scenarios were identified according to depth: in shallow zones, the health of P. oceanica meadows was related to the degree of anthropization along the coastline. In contrast, in deep zones, most meadows exhibited poor health, independent of both the degree of disturbance and the legal measures protecting the area. Working synergistically with the regional impact of increased water turbidity, local impacts from the coast were recognized as the main causes of the severe regression of most Ligurian P. oceanica meadows. We conclude that marine protected areas alone are not sufficient to guarantee the protection of P. oceanica meadows. We emphasize the need for a management network involving the Sites of Community Interest (SCIs) containing P. oceanica meadows.     

4D technology: where are we,and where are we going?

4D reservoir monitoring is now becoming established as a normal part of business in some companies, in some regions such as the North Sea, and for some applications, such as thermally enhanced oil recovery. Some spectacular technical successes have been reported, mostly in monitoring water floods. We are beginning to understand how to acquire and process surveys to achieve good results. There is still, however, much to improve in how we use 4D technology to capture its potential value in field management and still some way to go in the tool itself, to make it faster, cheaper and more sensitive to small production effects.     

Small galaxies are growing smaller

New telescope technology and major sky surveys are finding more and more dwarf galaxies. Steve Phillipps discusses how this growing population may hold the clues to understanding a range of galaxy collisions and interactions.     

New biocide-free anti-fouling paints are toxic

A number of new anti-fouling paints claimed to be more friendly to the environment, have entered the market since prohibition of biocide containing paints have been enforced in many areas. Leakage waters from five new anti-fouling paints were tested for toxic effects to the macro algae Ceramium tenuicorne and Ceramium strictum and to the crustacean Nitocra spinipes. A banned copper and irgarol 1051 containing anti-fouling paint was used as reference. Five of the six paints tested were toxic to all or some of the organisms after two weeks of leakage with EC50 ranging from 0.08 to around 2% leakage water and LC50 ranging from 1.1% to 88%. The toxicity of leakage water from these paints was still high after 16 weeks. We conclude that these paints contain substances toxic to common organisms in the coastal Baltic ecosystem. A silicone based paint did not exhibit toxic effects to the two organisms. We recommend that biological tests should be used to identify the most harmful products before they are released on the market.     

Try not to work too hard

Success in education, and subsequently in research, often comes from sustained hard work. Research is rewarding, satisfying and often a lot of fun, but it makes practitioners susceptible to working long hours at the expense of home and family life. How do researchers maintain a balance between work and leisure when careers are competitive, and posts scarce and often short-term? Sue Bowler ponders the outcomes of a work–life balance workshop.     

Earthshine: not just for romantics

Peter Thejll, Chris Flynn, Hans Gleisner and Andrew Mattingly explain how classic astronomical techniques, married to the latest technology, can be used to observe earthshine, and learn about Earth's climate, among many other things.     

Better models are more effectively connected models

Water‐ and sediment‐transfer models are commonly used to explain or predict patterns in the landscape at scales different from those at which observations are available. These patterns are often the result of emergent properties that occur because processes of water and sediment transfer are connected in different ways. Recent advances in geomorphology suggest that it is important to consider, at a specific spatio‐temporal scale, the structural connectivity of system properties that control processes, and the functional connectivity resulting from the way those processes operate and evolve through time. We argue that a more careful consideration of how structural and functional connectivity are represented in models should lead to more robust models that are appropriate for the scale of application and provide results that can be upscaled. This approach is necessary because, notwithstanding the significant advances in computer power in recent years, many geomorphic models are still unable to represent the landscape in sufficient detail to allow all connectivity to emerge. It is important to go beyond the simple representation of structural connectivity elements and allow the dynamics of processes to be represented, for example by using a connectivity function. This commentary aims to show how a better representation of connectivity in models can be achieved, by considering the sorts of landscape features present, and whether these features can be represented explicitly in the model spatial structure, or must be represented implicitly at the subgrid scale. Copyright © 2017 John Wiley & Sons, Ltd.