Changing oceans, changing diets: a summer of research in the Galapagos Islands
Written By: Maya Zeff (Fisheries Opportunity Fund Fellow 2024)
Climate change is driving rapid environmental shifts in marine ecosystems, leading to warmer and less productive oceans. Yet, our understanding of how these changes impact species interactions remains limited, particularly for food webs—ecological networks that depict feeding relationships among species—which are often studied as static interactions despite occurring in dynamic environments. Including realistic biological responses to environmental variation is essential to predict how ecological communities will adapt to future conditions.
The first chapter of my dissertation explores the relationship between primary productivity and dietary niche breadth (diet variability) through the niche width hypothesis. This hypothesis suggests that dietary niches constrict in areas of high productivity, promoting species coexistence, and expand in less productive environments, increasing competition among species. This phenomenon may be one mechanism underlying the widely observed positive correlation between primary productivity and biodiversity.
Fieldwork in the Galapagos
This summer, I investigated this hypothesis by collecting stomach content samples from four generalist fish species in the Galapagos Islands: Holacanthus passer (King Angelfish), Stegastes beebei (Ringtail Damselfish), Prionurus laticlavius (Razor Surgeonfish), and Ophioblennius steindachneri (Panamic Fanged Blenny). Collaborating with the Charles Darwin Foundation and a team from the University of Florida led by Dr. Robert Lamb, we embarked on multiple expeditions throughout July and August, gathering samples from over 300 individuals across a broad oceanographic gradient in the central archipelago.
Spearfishing with hand-thrown spears in one of the world’s most shark-dense areas was quite an adventure, made even more thrilling by giant moray eels that chased us through the water column and occasionally succeeded in stealing our catch. The Galapagos, shaped by the intersection of several major oceanic currents, presents unique marine gradients over compact geographical scales, making it an ideal setting for this study. Our study area spanned approximately 135 km, from the northeastern islands with warm, low-salinity waters that support reef-building corals and Indo-Pacific fish populations, to the rocky reefs of the westernmost islands with high primary production, rich algal assemblages, and high rates of endemism. This spatial gradient allows us to use high- temperature, low-productivity sites as proxies for future environmental conditions.
Next steps
We successfully exported these samples from the Galapagos National Park to the U.S. (no small feat!) and will now process them at U.C. Santa Cruz using DNA metabarcoding – a technique that identifies species in environmental samples through unique DNA sequences, much like product barcodes in a supermarket. This advanced method will enable us to determine the species-specific diets of these reef fish species with more precision than traditional approaches such as visual stomach content analysis. We plan to combine our molecular results with stable isotope data to gain a comprehensive understanding of their trophic position and dietary diversity. In addition to stomach contents, I also collected water samples at each site to determine available prey species, helping us understand whether reef fish actively select high-energy prey or if their diets simply reflect available resources.
Building connections for future research
As an aspiring long-term researcher in the Galapagos, this summer was instrumental in establishing connections with local researchers and fishermen. I regularly met with principal investigators at the Charles Darwin Foundation (CDF) which helped integrate me into a new research and conservation initiative focused on benefiting the Galapagos National Park. I also built relationships with local fishermen, collecting stomach contents from their catch, which will enhance our understanding of critical dietary resources for Galapagos fisheries.
Beyond research, I built relationships with community members by giving public lectures on my work in Spanish at the CDF, teaching English to young fishermen, and participating in a local music group. I also started collaborating with the lead of education programming at CDF, and we plan to conduct hands-on projects with youth at local elementary schools during my next trip. This initial field season was pivotal for my graduate career, allowing me to gather essential data, develop collaborations, and support my ongoing PhD endeavors. I am profoundly grateful to the Fisheries Opportunity Fund for enabling such a productive field season during my first year.
Maya Zeff (Ecology and Evolutionary Biology Graduate Student)