Florida’s marine terraces

In an article last year about Montana de Oro state park in California, I discussed how the land there includes a series of uplifted marine terraces. Those terraces are formed by a combination of geologic uplift at periodic intervals and the eroding action of the shoreline.

Well, here in Florida we’re pretty conversant with the eroding action of the shoreline. But for most of the east coast, at least, the forces of erosion and deposition are pretty much balanced. What the waves take away in the winter, they deposit in the summer, or vice versa. And in parts of the coast where the underlying limestone is exposed, you can actually observe the process of lithification taking place at the same time as you see wave action eroding the rocks!

A terrific example of this state of affairs can be found at Blowing Rocks Preserve, in Jupiter, Florida. It’s very exciting to see the waves crashing into the rocks, scouring them and undercutting the Anastasia limestone terrace (of Pleistocene origin); it’s easy to tell why this is called a high-energy coastline:

Wavesplosion at Blowing Rocks Preserve, Jupiter, Florida

Wave action undercutting terrace at Blowing Rocks Preserve, Jupiter Island, Florida.

The beach here is really something, with waves crashing into the limestone down below, while up above, the overwash creates tidepools where the sun and the salt water combine to cement the calcium carbonate shells of the marine mollusks into the cementitious rock known as coquina. The process can create some incredible combinations of erosion and formation at the same time, like this mini-arch in a tidepool on top of the limestone terrace:

Miniature arch forming/eroding at Blowing Rocks Preserve, Jupiter, Florida

Or this coquina “crater”; hard to tell whether it looks more like a volcanic or an impact crater on the moon, or perhaps the top of a fossilized sponge:

Coquina laminate formation at Blowing Rocks Preserve in Jupiter

The Anastasia formation, though, isn’t one of Florida’s recognized marine terraces; I’m not clear on why. Apparently, it’s just a limestone formation because it’s not exposed at the surface for its entire length? (See this article on raised beaches in Wikipedia, which equates the terms raised beach and marine terrace.)

Basically, marine terraces form through a combination of sea- and land-level changes with the action of erosion or deposition. Marine erosion creates features like wave-cut benches, sea cliffs, and rocky headlands, all of which are on display at Montana de Oro; not so much here in South Florida.

According to Anderson et al. (1999), marine terraces form when:

  • Sea-cliff retreat driven by wave erosion creates a wave cut platform.
  • The platform is abandoned when sea level drops leaving behind marine sediments covering a planar bedrock surface.
  • If tectonic uplifts rates are large enough, the old wave-cut platform has been lifted out of the surf zone by the next sea level highstand and the terrace is then preserved in the landscape.
  • Thus, a flight of marine terraces records the history of tectonic uplift and sea level fluctuation

Whatever the geologic explanation, exploring the beach is fun, and you can do it close to home, too. Further south in Palm Beach County, in my own town of Boca Raton, in fact, we can see a little bit of the formation at South Beach Park.

And, if you’re curious, Florida’s defined marine terraces, from Randazzo & Jones, are:

  • Silver Bluff (1—3 m elevation)
  • Pamlico (2.5—7.6 m)
  • Talbot (7.6—12.8 m)
  • Penholoway (12.8—21.3 m)
  • Wicomico (21.3—30.4 m)
  • Sunderland/Okeefenokee (30.4—51.8 m)
  • Coharie (51.3—65.5 m)
  • Hazlehurst (65.5—97.5 m)

One of these days, I might even be able to take some field trips to see them! But first, I need to digest the article by Alt and Brooks linked to above; it seems to explain some of the problems of interpreting marine terraces.

Fish oil

First, thanks to all of you on Facebook for wishing me a happy birthday; I did indeed enjoy a wonderful day. Seeing all your good wishes brought a smile to my face; I understand that’s somewhat out of character for the traditional man turning 40. So be it. I’m smiling, so thanks, y’all! Now, yesterday’s post was about WD40, which is NOT made of fish oil. So today’s post needs to be about, well, fish oil.

What is it good for? Everyone knows, nowadays, that fish oil is high in Omega-3 fatty acids, which apparently we need in order to be healthy. (Can you imagine what life would be like if we had only lean acids in our bodies? We’d probably all die of scurvy, or something.) These fatty acids bioaccumulate* in the fish (they don’t produce the acids themselves), which makes oil derived from fish high in the substances, and, it has been argued, has led to overfishing. (Industries such as commercial fishing, whose existence depends on denying this possibility, naturally tend to disagree. And some of their arguments are quite reasonable. But I’d hate to rely on the fox’s assessment of the health of the henhouse population…)

In addition to the fatty acids found in fish oil, the substance itself used to be used as a digestive aid, a medicinal tonic, and many other things. In addition to all these properties, it turns out that fish oil–in this case, a cupful of unrefined cod liver oil ($100+/gallon back in 1990)–is absolutely what you need to attract a large gathering of pelagic birds. Here’s how Rich Stallcup describes it in his incredibly useful book, Ocean Birds of the Nearshore Pacific (Point Reyes Bird Observatory, 1990):

On 27 August 1983, Terry Wahl, Bill Tweit, and I were 40 miles west of Westport, Washington, with a boatload of birders. The trip was going great, the water was glassy, and there were lots of birds. Four working shrimp trawlers were accompanied by over 5,000 shearwaters of five species, and we had seen Fork-tailed Storm-Petrels and several alcids on the way out. It was still quite early in the day, and Terry said, “Shall we go out to albatross habitat?” Sure! So we left this area of teeming activity, put the bow on the compass’s big green W, and powered west. Birdlife promptly declined, and there was only the odd Sooty Shearwater to be seen. When we got to about 50 miles, there wasn’t even that. I did a 360-degree scan. Nothing. Nothing but water, and Bill and Terry said, “This is the spot. Stop the engines.” Passengers were glancing at each other in wonder as gloppy, smelly, clear liquid bloop-blooped from plastic bottles, clinging to itself in patches, floating on the surface of the sea. I scanned. Nothing. Then, at a great distance, a wheeling albatross! Within ten minutes there were 61 Black-footed Albatrosses sitting near the boat, a Long-tailed Jaeger circled near by, and two Tufted Puffins came roaring in like spiraling, black footballs and splashed to stops. Sabine’s Gulls and storm-petrels appeared from nowhere. Everyone was impressed.

Of course, as Stallcup writes, it doesn’t always work this way, but when it does, I can just imagine the excitement that must come over the boat. And, in a few days, I hope to be able to see it, or something like it, with my own eyes, when I take my first pelagic trip.

When I get back, I’m going to try to drum up some interest in our local Florida birding group to motor out to the Gulf Stream some day to see what’s what. I just recently got some leads on local captains who might not mind a charter without the pressure of finding fish…

* Now, don’t get all excited just because I used the word bioaccumulation. The word may have come to prominence because it’s how environmental toxins like DDT move up the food chain, but the word, and the process itself, is fine, even necessary. We rely on bioaccumulation constantly. Can you imagine trying to go out and capture or manufacture each and every essential protein or nutrient in the food chain independently? Much better to rely on bioaccumulation in the food web, from primary producers (autotrophs like algae and phytoplankton) on up, to aggregate all of these packets, which we then just appropriate through the magic of killing and eating those animals in which the required substances bioaccumulate. Bioaccumulation, at its simplest, is just digestion.

Flying fish

Tony Gaston, in his Seabirds: A Natural History, speculates on escape flights of flying fish and flying squid, and it brings up something I need to investigate further:

The herding tactics of tropical tuna and dolphins may be an important factor in the development of short aerial escape flights of flying fish and flying squids, tactics presumably encouraged by the more rapid acceleration available to fish and squid in warm waters. A consequence of these escape flights is that some food becomes available to seabirds without contacting the water and this type of aerial foraging has been noted for tropical gadfly petrels, shearwaters, frigatebirds, tern, and the Red-footed Booby (Ballance & Pitman, 1999). Such opportunities are not available to cold-water seabirds. (111)

Now, I grew up in Los Angeles, and in the summers we would visit Catalina Island. The trip always involved an hour or two on the boat out of San Pedro, and along the way, we would frequently see flying fish. (I don’t recall seeing any flying squid, though.) The waters off L.A. are pretty darn cold, but nothing compared to, I suppose, the Atlantic (or Pacific) waters off Canada, which is where Gaston is from.

The questions I have are these:

  • Are there not enough flying fish off L.A. to be a resource for seabirds? (I certainly don’t recall any birds making meals of them, but then, it’s not like I was out there every day watching…)
  • Are the predatory fish off L.A. not able to stimulate sufficient volume of fish/squid needing to escape for them to become habitual prey items?
  • Are the waters off L.A. warm enough to qualify as providing “rapid acceleration,” which seems to be Gaston’s prerequisite for there to be flying fish in the first place?

One thing I’ve discovered since starting this thought process is that Catalina Island’s flying fish only fly in the summer, so there is definitely an element of heat and daylight involved; these fish must be migratory, and presumably follow their food resources, which must be limited by temperature or sunlight.

According to Wikipedia, the California flyingfish (either Cypselurus californicus, the genus name of which is not listed in my KPCOFGS, or Cheilopogon pinnatibarbatus californicus, of which the genus name, but not the specific epithet, is listed) is the largest species of the family. Apparently, adults are both epipelagic (meaning they hang out high enough in the water column for sunlight to penetrate, for there to be photosynthetic phytoplankton, etc.) and neritic (meaning they occur near shore [technically from the low tide mark to the edge of the continental shelf]). As such, they occur in those regions of the oceans most frequented by human observers (when was the last time you went below 200m deep?).

These fish are able to burst out of the water and glide (they don’t actually fly) thanks to their enlarged pectoral fins, which serve as airfoils. And, according to Gaston, temperature plays a role in their escape flights as well, providing them with enough metabolic energy for the demanding task of jumping out of the water and then staying out, working the air currents just above the water (the way many birds d0–most of us have seen pelicans surfing the air in front of the waves along the coast) to extend their glide, before eventually going back under (or being eaten by a lucky bird in the right place at the right time). Presumably they fly to avoid underwater predators; it must be frustrating to jump out of the frying pan only to wind up in the fire!

Which brings up a thought. Flying, frying. Maybe I should research frying fish for my next post? Or flame-broiled. Either way, yum!

June 8 is UN-designated World Oceans Day

The first United Nations-designated World Oceans Day is Monday, June 8. The theme that the UN came up with to inaugurate this special day is the awesomely inspiring slogan “Our Oceans, Our Responsibility.” Really conjures up the sense of fun and excitement we all feel when we head down to the beach, doesn’t it?

When I think of our oceans (or, to be more precise, our global ocean), I think seabirds:

Or sea oats:

Or perhaps even bikinis (do your own Google Image search if you want pictures!).

But, if you’re the UN, you think collective burden and guilt, heavy on the responsibility (and light on the enforcement). Read more

Ocean’s one

Despite the popularity of the recent films Ocean’s Eleven and sequel, Ocean’s Twelve, I have yet to see either blockbuster. I guess I’m just not a Clooney fan. But I am a fan of Ocean’s One. In fact, I just completed the Coastal Ecosystems module in the Florida Master Naturalist Program, meaning that I am now a certified Master Naturalist, having previously completed the Uplands and Wetlands modules. What’s Ocean’s One? Why, it’s the One World, One Ocean concept. Confused? Don’t be. You’ll find out more after the jump. Read more