You might have heard how energy is transferred from the sun through living organisms to become the food that we eat. Sunlight is used as energy in plants via photosynthesis, cows eat plants, and we eat cows (or at least some of us do). We set aside huge spans of acreage for the cows to eat this grass. These are managed by farmers to ensure their cows get the ultimate choice in grass. But what if these well-picked grass fields drifted away?
In the ocean, organisms that make up the base of the food chain, phytoplankton, are always on the move, shifted around by currents and wind. The animals that rely on phytoplankton as a food source must, therefore, be able to move as well. Zooplankton rely on phytoplankton for food, and also drift around in the ocean hoping to encounter sufficient food to survive. They enter the open ocean when nearshore fish and invertebrates spawn eggs and larvae. As these offspring grow and develop they spend various lengths of time in the water column. Some zooplankton spend only a few hours drifting in the water before settling down into their adult habitats. This creates a challenge for marine ecologists: With the exception of those few species that spend little time in the zooplankton, it is difficult to predict where most marine larvae will end up after spending their youth drifting around in the currents.
Larvae of the black rockfish (Sebastes melanops) are residents of the zooplankton that travel in the California Current System. Black rockfish larvae spend a period of 83-174 days in the plankton before settling into their adult habitats. During this time, larvae have been found to disperse as far as 120km from their birthplaces! Unfortunately, like many other species, black rockfish have experienced population crashes due to overharvesting. Since the 1990s adult populations from AK to CA have been in a state of decline. For such species with dwindling adult populations, the supply of larvae and juveniles to appropriate habitats are critical to population persistence. Consequently, black rockfish, as well as many other species are of great concern in marine conservation efforts.
Marine Protected Areas (MPAs) have been employed to reduce pressure on harvested marine species and support the rebound of shrunken population sizes. MPAs are regulated by the government so that all or part of the natural and cultural resources within it can be protected. It is crucial that they are well enforced so that illegal harvesting can be minimized and the MPAs can stay effective.
For those drifting organisms, it is difficult to pick the right size and location to effectively protect them. The MPAs need to be large enough to protect the maximum distance that the larvae move away from their birthplaces as well as account for the route they take, which can be from 50 km to over 100km long. Rather than creating one large MPA, one strategy is to create networks of MPAs. The sites of connected MPAs have to be close enough to be effective, but not so close that they become independently self-sustaining. In many countries, "networks" of MPAs have successfully been created. In California, MPA network design was adopted in the Master Plan for MPAs in 2008. These reserves directly or indirectly are connected to each other in an ecological sense and take into consideration larval and juvenile dispersal.
Designing MPA networks to protect species with dispersive larval stages is not easy. We need to understand more about the dynamic variations behind their dispersal to understand how the larvae connect the MPA’s to each other. This is why science-based policy design is crucial. It is the foundation of MPA guidelines that attempt to meet the goals of scientists, fisheries, conservationists, and the local community all in the context of our ever-changing global environment.
To learn more, please check out our linked videos above, and the following:
Botsford, Louis W., et al. "Connectivity, sustainability, and yield: bridging the gap between conventional fisheries management and marine protected areas." Reviews in Fish Biology and Fisheries 19.1 (2009): 69-95.
Moffitt, Elizabeth A., J. Wilson White, and Louis W. Botsford. "The utility and limitations of size and spacing guidelines for designing marine protected area (MPA) networks." Biological Conservation 144.1 (2011): 306-318.
About the authors:
Sarah is a UC Davis undergraduate studying wildlife, fish, and conservation biology who wants to bring the ocean and the rest of the natural world into dining room conversations for its and our own preservation.
Timothy is an undergraduate student at UC Davis interested in behavioral adaptations of marine animals and how they related to other organisms
Helen is a second year PhD student at UC Davis, investigating the population ecology and biological oceanography of coastal marine ecosystems with a focus on the behavior and transport of planktonic organisms.
For more from students studying at Bodega Marine Laboratory, see below!
- Oct 3, 2017 Ocean Acidification: Problems & Solutions Oct 3, 2017
- Oct 3, 2017 How do we protect ocean animals that drift with currents? Oct 3, 2017
- Jul 31, 2017 Jackie: Following stepping stones to environmental conservation Jul 31, 2017
- May 11, 2017 Linda: Understanding sea level rise in the past & future May 11, 2017
- May 5, 2017 Gabi: A personal legacy of commitment to marine science May 5, 2017
- Apr 7, 2017 Mimi: Dissolving Intertidal Organisms & Effects of Ocean Acidification Apr 7, 2017
- Dec 3, 2016 Adam: Studying past climates through (micro) fossils (Part I) Dec 3, 2016
- Dec 3, 2016 Adam: Studying past climates through (micro) fossils (Part II) Dec 3, 2016
- Oct 15, 2016 Priya: Happy 50th Birthday to Bodega Marine Lab! Oct 15, 2016
- Oct 9, 2016 Wendy: Mussel-ling My Way into Marine Biology Oct 9, 2016
- Sep 18, 2016 Walker: Reflections on a summer of research Sep 18, 2016
- Sep 12, 2016 Grace: Exploring research in marine science Sep 12, 2016
- Aug 23, 2016 Laura: A future teacher experiences marine research Aug 23, 2016
- Aug 17, 2016 Adam: Reflecting on the Past, in Years & Kiloannums Aug 17, 2016
- Aug 13, 2016 Amanda: Testing the waters in ocean chemistry Aug 13, 2016
- Aug 1, 2016 Grace: Carrying on a tradition of environmental stewardship Aug 1, 2016
- Jul 21, 2016 Walker: Seagrass, sediments, and a future in marine science Jul 21, 2016
- Jul 19, 2016 Welcome to the student research blog! Jul 19, 2016