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From Short Food Chains to Complex Interaction Webs: Biological Oceanography in 2025

Kelly J. Benoit-Bird*


Interaction webs, models that show which species in a community interact with each other and how strongly, are considered to be a cornerstone of modern ecology. Since interactions among species are a fundamental component of how communities and ecosystems function, interaction webs are central to a large number of ecological questions. Questions that have been addressed using interaction webs in benthic, terrestrial and lake ecosystems include:

  • Are large communities more or less resilient to environmental stress than small communities?

  • What is the maximum number of trophic levels likely to occur in any community?

  • Do changes in species abundance or composition at one trophic level create cascading effects to other trophic levels?

  • In a community subjected to anthropogenic perturbations, do decreases in the densities of some species lead to compensatory increases in the densities of functionally similar species, thereby preserving the ecosystem services performed by the community?

The emphasis in ecology on networks has highlighted the impor-

*

College of Oceanic and Atmospheric Sciences, Oregon State University



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OCR for page 118
From Short Food Chains to Complex Interaction Webs: Biological Oceanography in 2025 Kelly J. Benoit-Bird* Interaction webs, models that show which species in a community interact with each other and how strongly, are considered to be a corner- stone of modern ecology. Since interactions among species are a funda- mental component of how communities and ecosystems function, interac- tion webs are central to a large number of ecological questions. Questions that have been addressed using interaction webs in benthic, terrestrial and lake ecosystems include: • Are large communities more or less resilient to environmental stress than small communities? • What is the maximum number of trophic levels likely to occur in any community? • Do changes in species abundance or composition at one trophic level create cascading effects to other trophic levels? • In a community subjected to anthropogenic perturbations, do decreases in the densities of some species lead to compensa- tory increases in the densities of functionally similar species, thereby preserving the ecosystem services performed by the community? The emphasis in ecology on networks has highlighted the impor- * College of Oceanic and Atmospheric Sciences, Oregon State University 11

OCR for page 118
119 KELLY J. BENOIT-BIRD tance of the community on species-pair interactions. However, studies of pelagic marine ecosystems have emphasized primarily pairwise com- parisons of species sometimes between species that are not adjacent in the food web, making interpretation of results difficult. This focus on a few components in a system can be attributed to several factors: • the 3-dimensional nature of pelagic ecosystems; • the mobility of plants and all of the animals in these systems and thus the lack of a fixed reference point; • the specialized tools required to bring to the surface, image, or remotely sense the organisms, their characteristics, and their habi- tat; and • the inherent difficulties in making measurements and perform- ing manipulative experiments in the oceanic environment. As a result, comparisons in oceanic systems are often made between organisms that can be measured rather than those that are thought likely to interact. Continued development of new techniques and equipment to over- come these challenges is necessary, but not sufficient to move biologi- cal oceanography forward in the next few decades. In order to move from studies of short chains of organisms to ecological questions that can be addressed with the interaction web conceptual framework, several challenges need to be overcome. Because measurement of each type of organism in the ocean currently (and likely always will) requires a spe- cialized suite of techniques, few investigators are capable of making mea- surements of multiple trophic levels, which are quite different from the single-investigator studies that have proven effective at addressing these problems in other ecosystems. For example, phytoplankton are typically studied optically while fish are often investigated acoustically, two very different approaches requiring specialized equipment and data analysis skills. Studies of ecological questions at more than a single trophic level thus typically require multiple investigators. The academic reward system (e.g., promotion and tenure system) must be able to properly evaluate the contributions of members of these collaborative teams and reward members for this work equally to work carried out individually. While some progress in this area has been made, particularly in the historically interdisciplinary field of oceanography, these changes are not as obvi- ous in other disciplines (such as ecology) or at higher levels of academic administration. For example, if a department values and rewards col- laborative research how is this commitment to interdisciplinary study communicated to authors of external review letters and to committees in the dean’s or president’s offices? How are papers with multiple authors

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120 OCEANOGRAPHY IN 2025 evaluated? Do committees give credit for the time spent leading large research teams separately from paper output? These, and many other questions, need to be addressed in order to encourage young scientists to tackle large ecological problems requiring many investigators. The need for collaborative research to address important ecological problems is not a new one. Several large, ecosystem-scale studies have been funded in the last several decades, leading to significant advances in our understanding of a variety of pelagic marine ecosystems. How- ever, even in these big programs, investigators tended to emphasize their single organism of interest and small groups of investigators focused on comparisons of a few groups of organisms. The truly integrative studies needed to look at more than a few trophic levels simultaneously have proven exceptionally difficult both in planning and data collection and analysis. While specialized researchers will always be required to carry out specific measurements, interpret their data, and move techniques forward, to overcome these difficulties we also need broadly trained sci- entists focused on integration of results. To be effective, these individuals would need to understand the principles of the various instruments and data types, but would not be able to be technical experts in each. These individuals would play an important role in designing experiments so that comparable data could be collected on a variety of ecosystem com- ponents, would facilitate communication between groups that have their own specialized vocabulary, and would lead the synthesis stage of data analysis. This need for team leaders that specialize in synthesis presents two problems. First, how do we, a field primarily of specialists, effec- tively mentor these broadly trained students? Addressing this requires we rethink our educational paradigms and our traditional one-on-one apprenticeship approach to training graduate students. This is not an insignificant obstacle. Second, once we have trained these scientists, will they be able to find and succeed in research positions? This returns us to concerns about academic reward structure. Integrated studies of multiple types of organisms in terrestrial, ben- thic, and freshwater ecosystems have revealed how natural communi- ties are organized and have provided statements about whole commu- nities that are important for interpreting measures of a single species, understanding community processes, and predicting the effects of climate change. In studying the processes and patterns of communities in the pelagic ocean we face unique challenges, but they are not insurmount- able. Some challenges in integrated ecosystem studies will inevitably be addressed by the forward progress of instruments and techniques. There are, however, cultural barriers in academic reward structure and gradu- ate education that will not be overcome without a concerted effort from within the field of oceanography.