From afar, tidepools may appear as puddles of water among the rocky shore, covered by clamped up mussel communities and mats of seaweed looking displaced, dried and slack.
It isn’t until you crouch down and peer into these puddles that you see that they are filled with critters and teeming with life. Sea hares, octopuses, and crabs crawl along the rocks; macroalgae and surfgrasses soak up the sun; anemones, barnacles, and mussels filter-feed on the plankton and microbes within the pool. Up close, we now see that each tidepool constitutes a unique miniature ecosystem with a distinctive set of inhabitants and chemical reactions. Exposed for only a short period of time each day before the tide rushes back in, these dynamic pools are a treasure to examine by both curious bypassers and scientific researchers.
Tidepool foundation species, such as mussels, seagrasses, and certain macroalgae facilitate the establishment of the system’s balanced metabolism and play a key role in its resilience towards environmental pressures. However, habitat loss and climate have caused a decrease and shift in some intertidal foundation species, resulting in direct impacts on community structure, thermal buffering, and biogeochemical cycling. Elucidating the biogeochemical role of foundation species is crucial to understanding the ramifications that follow their loss within an ecosystem. Have you ever wondered what daily changes in tidepools (especially those invisible to our naked eye) rocky intertidal species are responsible for? Or, for people like me that are microbe-interested, have you ever wondered how the foundation species that live in these pools affect the pool’s microbial community and water chemistry? These are the research questions I am working to answer here in the tidepools at the Scripps Institution of Oceanography.
Before beginning any research, it’s essential that one becomes familiar with the environment and organisms they’ll be working with. Lucky for me, the Scripps Coastal Reserve’s tidepools are located a quick ten-minute walk from my lab; On any given day I am able to stroll down and monitor the pools and their tidal fluxes. This proximity to my field site makes me feel even more connected to and passionate about what happens to this habitat and its inhabitants. Although ecologists have been studying tidepools for decades, my project is the first co-occurring microbial and biogeochemical study on the rocky intertidal ecosystems of the Scripps Coastal Reserve. By combining marine ecology and biogeochemical measurements with modern molecular techniques, I am developing a comprehensive view of how tidepool foundation organisms influence the microbial community composition and metabolic function of this habitat. Further, I am examining the corresponding nutrient recycling and net community metabolism of these intertidal environments.
So what does a day of field sampling the tidepools entail? When the low tide exposes and isolates individual tidepools, I head out into the field with a lab partner, our bags packed with the necessary sampling equipment, and we set up the site. We measure physical parameters such as temperature, pH, and dissolved oxygen and utilize autonomous water pumps to collect water samples every hour that I later analyze for nutrient content, cell abundance, microbial DNA sequencing, and fDOM (fluorescent dissolved organic matter). Through this analysis, we measure both the production and consumption of important nutrients, like nitrogen and phosphorus, as well as bacterial count and community structure in the pools’ seawater.
The more acquainted I get with the tidepools, the greater my respect and appreciation becomes for these ecological mesocosms. My hope is that by studying their ecological function on a microbial level, I will elucidate the role of these invisible players and bring awareness to their critical role in these useful, yet often overlooked, intertidal habitats.
Written by Bibi Rennsen