Feature image photo credit:•$ Dr. Lauren Toth, USGS
Trying to predict how coral reefs will¶♦↓ respond to warming oceans and÷™ a changing climate may be conside•≥€♦red a daunting task for scientists. In the fa<£¶ce of this challenge, scientists at AOMΩ∞♣L recently published a study that characterizes the organisms and proc≈>'esses that lead to coral reef ac♠↓cretion (build up) and bioerosion (break dow₹§¥n) in the dynamic en€¥ vironments of the Gulf of Pa₩★namá and Gulf of Chiriqu>' ←í in the eastern Pacific.
So how does a reef ta☆©ke shape and create pillars, ridges, and mounta×πδinous structures? Ocean condition€"δs such as temperature, acidity, and avaπ€ilable nutrients in the water p →lay a role, as do mari✔¶ne organisms called “bioeroders” that™₹&α graze the coral for δ"algae (grazers), create ho₹£les in the coral surface ∏λ✔(microborers), or create holes in its int¶≤ernal structure (macroborers). Although gγφrazing and erosion diminish re₽ εefs, they also allow space>∑↕₹ for new coral to form through th✔&←e deposition of calcium carbonate–a process calle♠&"d “calcification.”
“Reefs are fighting ¶a battle on two fronts as the changing clima₹₩¶te decreases habitat growthαλ€π while simultaneously increasing ↑€erosion. The stakes of this battle are € ± high, with the very persistence ★γof reefs and the ecosystem services thatσ$↔₩ they provide in question,” said Ian Enochs, a r>☆←esearch ecologist at AOML • and lead author of the study.
Scientists studied the marine organis↔λms and processes mentioned above usi$↕±ng bioerosion accretion replicates (BARs) made♣'β₹ from stony coral (Porites) skeletons (the same material that mak÷>₹es up the reef), that w✔♥&βere deployed to reefs in the gulfs of Pan∞♦§amá and Chiriquí. After two yea£≠™ rs, they scanned the BARs§✔π using computed tomography (CT) to be₽€∞€tter understand bioerosion and accretion γβδat these reef sites. β☆∑≠;
The study revealed that in both gulfs, external €φbioerosion by grazers such as parrotfish andΩ&λ€ urchins was the major process al♥★tering coral reef habitat, with hig£✘her rates of erosion and habitat los•₩α☆s observed in the Gulf of C↑↓₩hiriquí. One difference in environmental f↑↕actors between the gulfs was the greater amount✔÷ of upwelling (movement of deeper cold nutβ÷rient-rich waters to the surface) in₹•± the Gulf of Chiriquí that may have provid↕↑£>ed a food source for₽∑$₩ calcifying animals, as well as accel> ←erated macroboring, lσ→eading to a less struc↑φ↑αturally stable reef developed on sediment (in↑Ωstead of solid reef material)σ↕λ♥.
Keeping up with sea level rise a↑✔nd other stressors brought on by c∞'¶limate change presents a challenge for reef♠≈ s struggling to grow and adapt↔®>π to changes in the environment. The inter•←action of reef structure, habitat biodivers♦↑δ↕ity, and ocean conditions cφ↑an lead to a variety of ecosystem outcomes that γ∏are difficult to predicε÷t. A holistic approach to examining the impact ♠αof environmental conditions on₩< all habitat-alterin☆♣↔φg organisms is key to understandiβ✘ng reef persistence in the eastern Pa₽®±cific and global oce✔an.
Reference:
Enochs, I.C., L.T. Tot♣<₽h, A. Kirkland, D.P."¥☆ Manzello, G. Kolodziej, J.↓∑$✔T. Morris, D.M. Holstein, A. Schlenz, C.J. Randaγ≠ll, J.L. Maté, J.J. Leichter, and R.B. Aronso≤€n. Upwelling and the β☆→≠persistence of coral-reef frameworks in the♣♠ eastern tropical Pacific. Ecological Monographs, 91(4):e01482, https://doi.org/10.1002/ecm.1482±←↔
(CREDIT: NOAA)