Search for: All records

Abstract Collective behaviors in biological systems such as coordinated movements have important ecological and evolutionary consequences. While many studies examine within‐species variation in collective behavior, explicit comparisons between functionally similar species from different taxonomic groups are rare. Therefore, a fundamental question remains: how do collective behaviors compare between taxa with morphological and physiological convergence, and how might this relate to functional ecology and niche partitioning? We examined the collective motion of two ecologically similar species from unrelated clades that have competed for pelagic predatory niches for over 500 million years—California market squid,Doryteuthis opalescens(Mollusca) and Pacific sardine,Sardinops sagax(Chordata). We (1) found similarities in how groups of individuals from each species collectively aligned, measured by angular deviation, the difference between individual orientation and average group heading. We also (2) show that conspecific attraction, which we approximated using nearest neighbor distance, was greater in sardine than squid. Finally, we (3) found that individuals of each species explicitly matched the orientation of groupmates, but that these matching responses were less rapid in squid than sardine. Based on these results, we hypothesize that information sharing is a comparably important function of social grouping for both taxa. On the other hand, some capabilities, including hydrodynamically conferred energy savings and defense against predators, could stem from taxon‐specific biology. 

Abstract Marine organisms and ecosystems face multiple, temporally variable stressors in a rapidly changing world. Realistic experiments that incorporate these aspects of physiological stress are important for advancing our ability to understand, predict, and manage their ecological impacts. However, the experimental systems needed to conduct such experiments can be costly. Here, we describe a low‐cost, modular control system that can be used with seawater sensors and actuators to dynamically manipulate multiple seawater variables. It enables researchers to run a variety of realistic multiple‐stressor, variable exposure experiments with a range of marine organisms. This tank controller system is based on the open‐source Arduino prototyping platform and features a custom‐made circuit board with a 16‐bit analog‐to‐digital converter, a real‐time clock, a MicroSD memory card reader, a high‐voltage transistor array, and solderless screw terminal connectors for easy connection of sensors, actuators, and power supplies. The assembly and use of this controller system does not require extensive electronics engineering or programming experience, and each module can be assembled for under 80 USD in parts. To demonstrate the system's capabilities, we present seawater manipulations from experiments involving (1) simultaneous manipulations of dissolved oxygen and pH; (2) fluctuating dissolved oxygen levels; and (3) a controlled stepwise decrease in dissolved oxygen at different temperatures. The low cost and high customizability of this Arduino‐based control system can contribute to expanding capacities for running global change experiments for researchers and students worldwide. 

Abstract Climate change is altering the intensity and variability of environmental stress that organisms and ecosystems experience, but effects of changing stress regimes are not well understood. We examined impacts of constant and variable sublethal hypoxia exposures on multiple biological processes in the sea urchinStrongylocentrotus purpuratus, a key grazer in California Current kelp forests, which experience high variability in physical conditions. We quantified metabolic rates, grazing, growth, calcification, spine regeneration, and gonad production under constant, 3-hour variable, and 6-hour variable exposures to sublethal hypoxia, and compared responses for each hypoxia regime to normoxic conditions. Sea urchins in constant hypoxia maintained baseline metabolic rates, but had lower grazing, gonad development, and calcification rates than those in ambient conditions. The sublethal impacts of variable hypoxia differed among biological processes. Spine regrowth was reduced under all hypoxia treatments, calcification rates under variable hypoxia were intermediate between normoxia and constant hypoxia, and gonad production correlated negatively with continuous time under hypoxia. Therefore, exposure variability can differentially modulate the impacts of sublethal hypoxia, and may impact sea urchin populations and ecosystems via reduced feeding and reproduction. Addressing realistic, multifaceted stressor exposures and multiple biological responses is crucial for understanding climate change impacts on species and ecosystems. 

Upwelling provides high amounts of nutrients that support primary production in coastal habitats, including giant kelp Macrocystis pyrifera forests. Growth and recruitment of kelp forests are controlled by environmental conditions, including temperature, nutrient availability, and storms, as well as biotic interactions. However, our understanding of juvenile persistence in the field is extremely limited, particularly the effects of grazing on the survival of early kelp stages and how environmental variability associated with upwelling dynamics may modulate grazing effects. We quantified herbivore impacts on juvenile M. pyrifera by deploying thirteen 24 h caging experiments approximately every 2 wk throughout the upwelling season in a giant kelp forest in Monterey Bay, CA, USA. Experiments spanned a range of natural environmental variation in oxygen, pH, and temperature, conditions known to affect grazer physiology and that are projected to become more extreme under global climate change. Overall, the herbivore community had a large effect on kelp survival, with 68.5% of juvenile kelp removed on average across experiments. Grazing increased throughout the season, which was most strongly correlated with decreasing monthly oxygen variance and weakly correlated with decreasing monthly pH variance and increasing temperature. This suggests that large swings in oxygen during peak kelp recruitment in spring may provide a temporal refuge from grazing, allowing kelp to reach larger sizes by late summer and fall when upwelling has relaxed. This study highlights the potential of current environmental variability, and its predicted increase under future scenarios, to mediate species interactions and habitat persistence.