Nathalie B. Reyns

Complexity and simplification in understanding recruitment in benthic populations

Research of complex systems and problems, entities with many dependencies, is often reductionist. The reductionist approach splits systems or problems into different components, and then addresses these components one by one. This approach has been used in the study of recruitment and population dynamics of marine benthic (bottom-dwelling) species. Another approach examines benthic population dynamics by looking at a small set of processes. This approach is statistical or model-oriented. Simplified approaches identify “macroecological” patterns or attempt to identify and model the essential, “first-order” elements of the system. The complexity of the recruitment and population dynamics problems stems from the number of processes that can potentially influence benthic populations, including (1) larval pool dynamics, (2) larval transport, (3) settlement, and (4) post-settlement biotic and abiotic processes, and larval production. Moreover, these processes are non-linear, some interact, and they may operate on disparate scales. This contribution discusses reductionist and simplified approaches to study benthic recruitment and population dynamics of bottom-dwelling marine invertebrates. We first address complexity in two processes known to influence recruitment, larval transport, and post-settlement survival to reproduction, and discuss the difficulty in understanding recruitment by looking at relevant processes individually and in isolation. We then address the simplified approach, which reduces the number of processes and makes the problem manageable. We discuss how simplifications and “broad-brush first-order approaches” may muddle our understanding of recruitment. Lack of empirical determination of the fundamental processes often results in mistaken inferences, and processes and parameters used in some models can bias our view of processes influencing recruitment. We conclude with a discussion on how to reconcile complex and simplified approaches. Although it appears impossible to achieve a full mechanistic understanding of recruitment by studying all components of the problem in isolation, we suggest that knowledge of these components is essential for simplifying and understanding the system beyond probabilistic description and modeling.

Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX

A combination of historical bivalve surveys spanning 30–50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration.

Specialization versus diversification: A trade-off for young scientists?

Owing to the inherent links between the fields of study that make up the environmental sciences (e.g., terrestrial, aquatic, and atmospheric branches), and because of the growing need to better understand how human actions translate into global change, there is increasing demand for interdisciplinary research where Earth scientists with different academic training or backgrounds come together and approach projects in novel ways. In theory, interdisciplinar research teams are composed of researchers with complementary skills and are thus able to tackle larger research questions or problems. In this essay, we discuss the perceived trade-offs that young scientists face when specializing or diversifying their research programs to best prepare for participation in such interdisciplinary research. An effective member of an interdisciplinary team should have expertise in at least one discipline. For a young scientist at the start of his or her career, a period of specialization is necessary in order to be perceived as an expert by potential collaborators. At the same time, the success of an interdisciplinary collaboration may be enhanced by an individuals ability to understand and communicate about subject matters outside of his or her immediate area of expertise. For a young scientist, this implies that one should also broaden the scope of ones field of expertise and diversify. Thus, young scientists may prepare themselves for participating in interdisciplinary research projects by either specializing or diversifying their research programs, although a potential trade-off between both may exist.