Exposure to artificial light at night (ALAN) alters RNA:DNA ratios in a sandy beach coleopteran insect.

Coastal habitats worldwide, including sandy beaches, are becoming increasingly exposed to Artificial Light at Night (ALAN). Despite the spread of this global stressor, research assessing ALAN potential impacts remain scarce, particularly at the molecular level. This study addressed this gap by assessing the influence of ALAN on the physiological condition of the sandy beach insect Phalerisida maculata Kulzer (Coleoptera, Tenebrionidae). RNA:DNA ratios were used here as a proxy of the insect's nutritional condition in laboratory trials that lasted 20 d. Insects were exposed to two representative ALAN conditions (either 60 or 120 lx) and compared with those maintained in a natural daylight/night cycle (0 lx at nigth; control). After the trial, organisms from each treatment were frozen in liquid nitrogen and standard protocols were followed to estimate RNA, DNA and RNA:DNA ratios. Estimates of RNA:DNA ratios from insects maintained in control conditions were significantly higher (P < 0.05) than those from insects exposed to ALAN. The reduced nutritional condition of insects exposed to light pollution is explained by the lower in situ biosynthetic capacity in these organisms resulting from a reduction in their feeding. ALAN likely altered P. maculata normal locomotor activity, which takes place primarily at night, forcing the insects to remain buried in the sand for extended periods of time. As ALAN continues to spread along coastlines worldwide, there is a likelihood of growing impacts on these and other species living on sandy beaches and other coastal habitats.

Environmental refuges increase performance of juvenile mussels Mytilus chilensis: Implications for mussel seedling and farming strategies.

Estuarine ecosystems are characterized by a wide physical-chemical variation that in the context of global change scenarios may be exacerbated in the future. The fitness of resident organisms is expected to be influenced by such variation and, hence, its study is a priority. Some of that variation relates to water vertical stratification, which may create "environmental refuges" or distinct layers of water with conditions favoring the fitness of some individuals and species. This study explored the performance of juvenile mussels (M. chilensis) settled in two distinctive water depths (1 m and 4 m) of the Reloncaví fjord (southern Chile) by conducting a reciprocal transplants experiment. Salinity, saturation state and the contents of CO3 in seawater were among the factors that best explained the differences between the two layers. In such environmental conditions, the mussel traits that responded to such variation were growth and calcification rates, with significantly higher values at 4 m deep, whereas the opposite, increased metabolic stress, was higher in mussels raised and transplanted to the surface waters (1 m). Such differences support the notion of an environmental refuge, where species like mussels can find better growth conditions and achieve higher performance levels. These results are relevant considering the importance of M. chilensis as a shellfish resource for aquaculture and a habitat forming species. In addition, these results shed light on the variable responses exhibited by estuarine organisms to small-scale changes in the characteristics of the water column, which in turn will help to better understand the responses of the organisms to the projected scenarios of climate global change.

The energetic physiology of juvenile mussels, Mytilus chilensis (Hupe): The prevalent role of salinity under current and predicted pCO2 scenarios.

As a result of human activities, climate forecasts predict changes in the oceans pCO2 and salinity levels with unknown impacts on marine organisms. As a consequence, an increasing number of studies have begun to address the individual influence of pCO2 and salinity but much remains to be done to understand their combined effects on the physiology and ecology of marine species. Our study addressed this knowledge gap by measuring the influence of current and predicted levels of pCO2 (380 and 1200 ppm, respectively) and salinity (20, 25 and 30 psµ) on the energetic physiology of juvenile mussels (Mytilus chilensis) from the south-eastern Pacific region. Our results indicate that a reduced salinity caused a significant reduction in clearance rate, absorption efficiency and scope for growth of this species. Meanwhile, an increase in pCO2 levels caused a reduction in excretion rates and interacted significantly with salinity in the rate of oxygen uptake measured in the mussel. These results suggest that potential changes in salinity might have a direct role on the physiology of M. chilensis. The effect of pCO2, although less prevalent among the variables measured here, did interact with salinity and is also likely to alter the physiology of this species. Given the ecological and economic importance of M. chilensis, we call for further studies exploring the influence of pCO2 across a wider range of salinities.

Light pollution reduces activity, food consumption and growth rates in a sandy beach invertebrate.

The continued growth of human activity and infrastructure has translated into a widespread increase in light pollution. Natural daylight and moonlight cycles play a fundamental role for many organisms and ecological processes, so an increase in light pollution may have profound effects on communities and ecosystem services. Studies assessing ecological light pollution (ELP) effects on sandy beach organisms have lagged behind the study of other sources of disturbance. Hence, we assessed the influence of this stressor on locomotor activity, foraging behavior, absorption efficiency and growth rate of adults of the talitrid amphipod Orchestoidea tuberculata. In the field, an artificial light system was assembled to assess the local influence of artificial light conditions on the amphipod's locomotor activity and use of food patches in comparison to natural (ambient) conditions. Meanwhile in the laboratory, two experimental chambers were set to assess amphipod locomotor activity, consumption rates, absorption efficiency and growth under artificial light in comparison to natural light-dark cycles. Our results indicate that artificial light have significantly adverse effects on the activity patterns and foraging behavior of the amphipods, resulting on reduced consumption and growth rates. Given the steady increase in artificial light pollution here and elsewhere, sandy beach communities could be negatively affected, with unexpected consequences for the whole ecosystem.