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Monica Medina – A New Look at Coral Reef Ecology

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Monica Medina – A New Look at Coral Reef Ecology

Medina and her dive team

A recent arrival in the Biology department’s team of marine scientists has exchanged her Californian lifestyle at the University of California Merced campus with the forests and valleys of Pennsylvania. She hasn’t however, forfeited trips to the Caribbean and Panama to conduct research on coral reefs. Welcome to the working world of Monica Medina where scuba diving in tropical waters is a routine part of her field season.  Medina visits the newest of her research sites in Panama once a year when the corals are spawning. She works with an international team of biologists who have followed this particular transect of the reef for over a decade, to acquire precise genomic data and examine the microbial diversity of this coral ecosystem.

Medina’s interest is concentrated in two main areas concerning the health of coral reefs in the face of global climate change. At the heart of the ecosystem is the onset and breakdown of a symbiotic partnership. During the summer the corals spawn and release gametes into the water column. Samples are collected, enabling various experiments to be carried out back in the lab. One area of research involves examining the relationship between unicellular algae in the genus Symbiodinium and the coral it interacts with. Medina is looking at this interaction to establish when the onset of symbiosis in coral larvae takes place.  The juvenile corals are receptive to many different strains of algae and Medina is interested in establishing what genes are differentially expressed when a strain is accepted or rejected. In contrast to the juveniles, the adult coral will sustain very few Symbiodinium genotypes, so at which point does the coral become choosy and what triggers this change?

The second issue is to find out how symbiosis affects the breakdown of adult coral - bleaching – which occurs when coral is stressed by higher water temperatures, and also when disease is a factor.  As the corals bleach and recover, Medina and her team take samples and freeze tissue for RNA sequencing. With a team of six doctoral students and two post-doctoral researchers Medina has many hands to assist with collection at the field sites and experimentation back in the lab.

In order to keep the collection of coral samples to the minimum her team is utilizing a species of jellyfish - Cassiopeia - that behaves in a similar way to coral in utilizing algal symbionts. This system has a number of benefits: it allows them to bleach and infect the jellyfish year round in the lab as well as to recruit undergraduate students who can gain valuable research experience from working with this system. Examination of the developmental phenotype is also possible after the introduction of the Symbiodinium algae metamorphosis takes place and ephyra (baby jellyfish) result.  Symbiosis as a mechanism to induce development is poorly known and this area of research may have implications in other areas of biology.

Very few faculty members limit their focus to one specialization without considering the broader implications and Medina and her team are also interested in the issue of biomineralization.  Algal symbiosis provides extra energy to the coral host enabling calcification of the skeleton to increase reef accretion. Coral hosts return inorganic nutrients to ‘feed’ the algae. To overcome the difficulties of examining the early changes in coral larvae, Medina’s lab is using alternative models to examine key protein hubs in calcification networks. The mantle tissue involved in shell growth in snails, for example, shares conserved proteins with many animals including corals. Snails provide a tractable lab system to study some of these biomineralization proteins.

The future of the coral reef ecosystem depends on symbiotic partnerships and Medina’s genomic perspective is contributing to the scientific evaluation of marine environments and how they are responding to climate change.

[MH]