Tuesday, March 20, 2018

FL Keys Marine Lab field trip, Spring 2018

Every semester I take my FGCU Marine Ecology class to the Florida Keys Marine Laboratory for a few days of educational snorkeling. I bring lots of marine life guidebooks and encourage the students to identify all the organisms they see. I think learning what species you're looking at is the first step towards assessing the state of the ecosystem. It's also something I enjoy as a hobby, so I really look forward to photographically "collecting" new-to-me species.

This year I "scored" a few species that I was particularly excited about: Ocellate Box Crab, Batwing Coral Crab, Golfball Coral, Barred Hamlet, Reef Butterflyfish. You can find them and lots more, with descriptions, in the album of all the pictures I took this year, which is posted on my science facebook page.

The next part of this post may fall into the "too long didn't read" category for some people, but I felt like I should share these impressions about how the underwater habitats in the Florida Keys are doing lately, what with Hurricane Irma and some man-made problems, as well. Below is a summary of the changes I've seen at five of our regular snorkeling sites.

Site 1- KML Cove. The Keys Marine Lab is on the shallow, sheltered waters of Florida Bay. We do our first snorkeling activity in a little cove behind the lab. The cove has lush beds of seagrass and algae, with a few sponges and small, inconspicuous corals. I haven't noticed much change in the cove since Irma, besides some sunken branches and debris. However, there have been major impacts further north in Florida Bay, where lots of seagrasses died out due to salinity changes, murky water, and algae blooms. While boating through the Bay this spring we hit a line of the "post-Irma bad water," which was olive brown and totally opaque. Damage in Florida Bay can have a harmful domino effect, because when seagrass dies, it releases nutrients that cause algae blooms, which cause more seagrass to die, which releases more nutrients, and so on.

Site 2- Zane Grey Creek. This is a mangrove-lined, tidal channel that drains Long Key's shallow, internal lagoon. The creek waters can be tea-stained with tannins from seagrass and mangrove detritus, but they are generally fairly clear and high in salinity. Strong ebb-tide and flood-tide currents through the creek, coupled with its stable, high salinity, allow for the development of rich communities of filter-feeding organisms on the mangrove roots. In past years, sponges of all sorts- purple, blue, orange, white, brown, green, etc., covered the mangrove roots, and truck-tire sized loggerhead sponges studded the creek bottom. Those ALL died after Irma. Every single sponge. We speculate that they were done in by a combination of fresh water from the extreme rains, and the choking clouds of brown silt that were suspended in the water all around the keys in the weeks after Irma. I thought some sponges might recolonize the creek between November 2017 and March 2018, but they didn't. KML staff said that something similar happened in the creek after Hurricane Wilma in 2005, and it took about 7 years for the sponges to recover.

Site 3- Cheeca Rocks is a "patch reef" in shallow water relatively near the shore of Islamorada. It's designated as a Special Protected Area (SPA), which means that there's no fishing or collecting allowed there. It's unusual for a near-shore reef in that it still has a relatively high percentage of living hard corals, including the massive brain corals and star corals responsible for building the rocky structure of the reef. Since I first visited Cheeca Rocks in 2012 it has suffered from coral bleaching and disease outbreaks, which have killed or partially killed a substantial portion of the coral colonies. For example, some types of brain coral and maze coral are no longer present there. That said, Irma didn't seem to kill any corals at Cheeca Rocks that weren't already dead before the storm, although it did tip some colonies of star coral on their sides, and it moved sand that partially buried or un-buried portions of the reef. The main difference I noticed at Cheeca Rocks between November 2017 and March 2018 was a big increase in the amount of macroalgae (seaweed) on the reef. The algae and other soft-bodied organisms were probably blasted away by Irma's waves, but later took advantage of the vacant real-estate to recolonize. Algae compete with corals for light and space, so too much algae can harm reefs, especially if its growth is fueled by excess nutrients from pollution, or if the reef lacks algae-eaters like parrotfish and urchins.

Site 4- Alligator Reef. The saddest reef site, ironically, was the furthest offshore one that ought to be the most pristine and beautiful. Alligator Reef is a SPA like Cheeca Rocks, so it does have a lot of fish. It just has very little hard coral. Less than 1% of the sea bottom there is hard coral, whereas on a healthy reef it should be >30%. When I first visited Alligator Reef in 2012 there were at least a few colonies of hard coral studding the reef top. Those colonies included one endangered Elkhorn Coral, a remnant of the forest of Elkhorn Coral that covered most of Alligator Reef before it began dying off in the 1980s. Even though the reef was basically "dead" before Irma, inasmuch as it didn't have enough hard coral cover to keep its mineral growth rate apace with the rate of erosion, it at least looked pretty because there were lots of soft corals, sponges and algae on the reef skeleton. Irma swept those organisms away, highlighting the reef's depressing desolation. In November 2017 Alligator Reef just looked like a dusty concrete ledge. Since then the fast-growing algae have recolonized, and some of the soft corals and sponges are beginning to recover, as well. The hard corals really seem to be gone for good, though, which is crazy and awful.

Site 5- Stag Party. Staghorn Coral is a relative of Elkhorn Coral. It looks like deer antlers. It used to be one of the most common corals on Caribbean reefs, but it started dying out along with Elkhorn Coral in the 1980s. The "Stag Party" snorkel site was one of the few places where one could still reliably find Staghorn Coral in the 2000s, but bad bleaching and disease events in 2014, 2015, and 2016, related in part to mismanagement of water flow to the Everglades and Florida Bay, have almost completely wiped it out. I snorkeled the site for about 30 minutes this month before I found even one remnant patch of sick and pale looking Staghorn Coral. There have been big hopes that this potentially fast-growing coral will make a comeback, but I don't think it will happen unless we take big steps to fix our water pollution and climate change problems.