Pros vs Cons: Florida’s Sargassum Bloom
Algae are credited by science for a myriad of critically important ecological attributes, but its coexistence and potential harmful impacts tend to enter our daily lives unexpectedly. We rarely think about algae unless it’s a derogatory endeavor — cursing a wad of the stuff clinging to the hook of a favorite lure, plopping the hook repeatedly into the water to try and part ways with the slime to make the next cast a clean one.
Algae become more tangible experienced firsthand. Maybe as overgrowth of blackish-green leafy-goo drooping from a neglected crab trap reminiscent of Cousin Itt. Maybe a calm morning where the water was umber red with thousands of small fish floating dead on the surface.
You might also recall a toxic blue-green algae bloom along Florida beaches on the July 4th holiday or this year’s red tide event where Karenia brevis, a marine dinoflagellate, caused fish kills.
THE GREAT ATLANTIC SARGASSUM BELT
If the algal intruding scenarios above are not enough to make you wonder about primordial ooze, its role in the circle of life and the condition of our surface waters, then throw in another wild card — The Great Atlantic Sargassum Belt (GASB). A 5,000-mile intermittent raft of floating macroalgae that has gone rogue. When viewed by satellite mapping efforts from space, it resembles a new oceanic constellation stretching from West Africa to the Gulf of Mexico. In 2018, it contained greater than 20 million metric tons of flotsam, dominated by Sargassum natans and S. fluitans, innocuous macrophytic brown seaweed, common to the Sargasso Sea.
First reported by Christopher Columbus in the 15th century, the algae grew this year to a record density of about 13 million tons (March 2023). Sargassum biomass estimates by the USF Optical Oceanography Laboratory include a prediction that the GASB will likely be the largest macroalgal bloom ever recorded. You can follow the bloom online through the Sargassum Watch System (SaWS, optics.marine.usf.edu/projects/saws.html).
MACROALGAE GONE ROGUE
A new algal bloom of this size threatens public health and local beachside economies. Although the algae are not known to produce toxins, it accumulates on beaches, decays and emits gasses (like H2S, NH3, CO2, CH4) that smell similar to rotting eggs. The foul mess is also a haven for fecal bacteria and can give rise to anaerobic zones in near-shore habitats. The GASB, first noticed in 2011, may be driven by ocean circulation, upwelling and as a result of Amazon River discharges.
Scientists believe the GASB may not be an anomaly and could become the new norm — a prolonged and expanding drift of pelagic poo.
IT’S NOT ALL BAD NEWS
Macroalgae are ecologically important components of marine ecosystems. For example, algae collectively produce somewhere between 50-80% of the available oxygen here on Earth and they may represent significant carbon sinks. The full list of positive macroalgal attributes is much longer, but let’s focus on what we love most — big, toothy, wickedly fast, hungry pelagic fishes that utilize sargassum macroalgal rafts in open oceanic waters.
Structural macroalgal rafts are, without doubt, an important habitat for fish and the prey they feed upon. It is also a renowned habitat utilized by those of us who fish offshore. As many as 81 species of fish have been identified from sargassum rafts. Amongst healthy floating sargassum, a diverse assemblage of juvenile fishes feed heavily on still smaller fishes, crustaceans and other invertebrates, while they shelter within and beneath the algae’s physical structure to escape predation.
Predatory fishes such as filefishes, triggers, jacks, dolphin, tripletail, cobia, barracuda, mackerels and tunas, swordfish and billfishes are also commonly associated with the floating algae.
Charter captains know how to examine sargassum rafts to ensure that it is functioning to attract and hold quality fish. They simply collect sargassum from the water and give it a shake onto the deck. There should be plenty of visible life thriving amongst the algae if they plan to work that particular area of water.
MORE WEEDS, MORE FISH?
In addition to available food and shelter, adults of some pelagic fishes use sargassum as a spawning substrate or as a nursery area for larvae and juveniles. Most notable among them are the flying fishes that are a major component of the diet of the large oceanic fishes mentioned above.
It’s possible there could be increased fish production connected with the expansion of holopelagic sargassum. More weeds, more fish? Maybe, maybe not — but let’s hope so. It’s anyone’s guess how that relationship between fish and algae might change with such an enormous increase in algal biomass within the GASB. However, it’s important to consider that ecosystems change due to anthropogenic drivers rarely turn out well for natural systems.
EYES ON THE WATER
Captains are our eyes on the water. They are sentinels that can report environmental changes as they are happening in real time. A great example is the FWC Fish & Wildlife Research Institute partnership with Community Scientists that helps monitor Red Tide. Captains for Clean Water have also used community partnerships in its success to influence policy makers and those who wield power and control purse strings in Tallahassee. Their message includes opportunities to get involved and help protect the environment we all depend on.
Bloom and doom be damned. While we anticipate the arrival of sargassum to our beaches, Florida will plan a response to yet another imminent threat from harmful algae.
Science will certainly do its best to tease apart the confounding environmental factors driving expansion of the GASB. The engineers might even figure out how to manage the impacts effectively. Experience, time and relentless attention to nature are something we can all agree is necessary to protect what we love most out on the water.
It’s not an entirely dire environmental situation and it’s never too late to turn things around for the better. I believe that captains matter, and that nature is resilient — if we just give it a chance.
Source: https://floridasportfishing.com/pros-vs-cons-floridas-sargassum-bloom/
