How Will Climate Change Impact Fishing?

As our waters warm, seas rise and fish move. Climate change impacts fishing below the surface.

Climate change affects our oceans, particularly sea level rise, which, in turn, affects things below the ocean surface, where the results are harder to see. Aquatic life adapts to these changes. Some species may migrate in search of the environment that best suits them. Other species may become less productive and may even face extinction.

Decreasing populations will impact commercial, sport and recreational fisherman, but most importantly, a vital food supply. Marine and coastal fisheries are a $200 billion industry and support nearly two million jobs; any major changes are concerning.
Climate change impacts the oceans a number of ways. Of paramount importance for sea life is increasing water temperatures.

Troubling Times

In fact, the ocean is warmer today than at any time since record-keeping began in 1880. Water has a high heat capacity. It is believed that the oceans store 90 percent of the excess heat generated by the greenhouse effect. On an even more troubling note,
the rate at which the oceans are warming is also accelerating. This has a harmful effect on aquatic organisms who are sensitive to relatively small variations because water temperatures rarely change.

A graphic outlines how dead zones form in our waters.

In addition to increasing water temperatures, there is more carbon dioxide in the atmosphere that dissolves into the water; seawater is becoming more acidic. This means less calcium carbonate for coral reefs to build, a major factor in the destruction of these reefs. Melting ice caps and glaciers, as well as the physical expansion of water at higher temperatures, have caused sea levels to rise, which certainly affects the spawning areas of many fish species.

Variations in seasonal rainfall and individual storm events cause local changes in water
conditions both in terms of temperature and salinity. The amount of dissolved oxygen water can hold, a critical factor for all underwater life, is a function of temperature. Warm water can’t hold as much oxygen, another negative factor for undersea life. The oxygen-devoid “dead zones” we see in the Gulf and elsewhere will likely intensify and expand, just another way that climate change impacts fishing.

High Temps = High Stakes

Nearer the shore, the stakes are even higher. Many fish, such as red drum and sea trout, use bays and estuaries as breeding grounds. Shrimp, oysters and blue crabs are dependent upon them. Unfortunately, the risk of environmental changes is even greater here. With shallow water, temperature changes are more pronounced and happen more rapidly. Salinity is also significantly affected. Heavy rains will bring an influx of fresh water and lessen salinity.

Drought conditions will diminish freshwater inflow and increase salinity. Pollution, especially nutrient pollution, is a major concern in some areas. In conjunction with warmer water temperatures, this will lead to more harmful algal blooms such as red tide. Stronger storms can produce more damage, and the rise in sea level can dramatically alter habitats.

Even the increase in air temperature can change habitats. For example, along the Texas coast and the Florida east coast, black mangroves are moving northward and replacing
cordgrass marshes. One comprehensive study looked at the predicted geographic distribution of nearly 700 marine species in the Atlantic and the Pacific out to the year 2100 for a number of different climate scenarios. Most, but not all, species shifted poleward, generally following the adjacent coastline.

Many species were forecast to migrate more than 500 miles from current locations because of the higher temperature predictions. A study on the effects of climate change on the Gulf of Mexico fish populations yielded mixed results with some species benefiting and some suffering. Red and gray snapper and red porgy benefited from habitat expansion, whereas, Spanish mackerel were likely to move to deeper, cooler waters. Another study forecast pink shrimp Gulf habitat to decline by 70 percent by 2100. It also predicted that species from the Caribbean may move north into the Gulf.

The Times, They Are A-Changin’

Changes are already taking place. The oyster catch along the Gulf coast of Texas is down significantly. Butterfish are replacing herring in the Gulf. Atlantic cod have decreased by more than a third. Black bass, which concentrated off the North Carolina coast, are now most abundant off New Jersey. The lobster population in the Gulf of Maine has increased dramatically with warmer water temperatures, and blue crabs have also moved in.

Fisheries are among the first industries affected by climate change. Coastal communities feel the brunt of the economic impacts. Fishermen may have to travel much farther to
find the preferred species or just give up on it. Regulations on fishing that worked in the past will become obsolete if not counterproductive. Jurisdictional disputes, even up to
the international level, may result. The increase in ocean temperatures will likely continue, and the effects on sea life may even become more pronounced.

Climate Change Impacts Fishing

The NOAA Fisheries Climate Science Strategy was developed to provide pertinent climate information and predictions to those involved with fisheries so they can prepare to deal with and manage climate changes. In conjunction with Rutgers University, NOAA Fisheries developed the OceanAdapt web-tool to provide easy access to information about the distribution of marine species involved in commercial and recreational fishing over time. Wise management of our ocean resources is our only option. We must keep a constant watch on what is going on under the water’s surface and change policies accordingly.

By Ed Brotak, Southern Boating June 2019

El Niño and La Niña

What’s the difference between El Niño and La Niña?

Long before meteorologists “discovered” the El Niño (EN) phenomenon, fishermen in Chile and Peru were well aware of it. Typically, the fishing there was great. The deep, nutrient-rich waters attract bountiful marine life, but every few winters, things would change dramatically. It got much warmer, it would rain in the coastal desert region and the fish would leave. A flood of warm water from the west would push the bountiful cold water to the south. Since this was often most pronounced around Christmas, they called it El Niño for “the boy.” La Niña (LN) is the female equivalent.

The Boy and the Girl

The El Niño and its counterpart, La Niña, have major impacts on the weather around the world, but did you know they are actually oceanic circulations? To explain the EN/ LN cycle, one must go to the tropical Pacific Ocean. With the cold Humboldt Current and associated upwelling, the eastern Pacific waters off of South America are abnormally cold, over 10ºF colder than sea surface temperatures in the western Pacific. In the tropics, the prevailing (or trade) winds tend to blow from east to west and drive the ocean surface waters with them. The North Equatorial Current flows westward from the South American coast across the Pacific to Oceania in the Asia-Pacific region.

There are times when the trade winds weaken and, consequently, so does the equatorial current. Warm water, which used to be transported across the Pacific, now begins to “back up.” Water temperatures then begin to abnormally rise in the central Pacific and work its way back to the South American coast. This warming can amount to a two- to six-degree increase over normal conditions, a significant departure for this vast amount of water. This is the El Niño.

With La Niña, the trade winds and equatorial current are abnormally strong. Larger than normal amounts of warm water is transported away from the central and eastern Pacific, and water temperatures there become unusually cool. Both El Niño and La Niña events tend to develop in the spring, hit their peak intensity in the winter, then weaken the following spring, about a 9- to 12-month average lifespan.

Cycle(s) of life

Meteorologists often refer to the EN/LN cycle as the El Niño Southern Oscillation (ENSO). The Southern Oscillation deals with the atmospheric pressure changes in the Pacific region that accompany the two phases. In addition to the two extremes, we can have more average conditions (called ENSO neutral).

So, how and why does the EN/LN cycle affect our weather? The tropical oceans are a vast storehouse of heat or energy. They transfer some of this energy to the air which goes high into the atmosphere and “feeds” powerful jet streams. Changes in the tropics can reach well into the mid and high latitudes.

The effects of the EL/LN cycle are most pronounced in winter. The warmth of El Niño fuels a strong, southern jet stream that starts in the eastern Pacific and produces an active southern storm track that blocks cold air from entering much of the U.S. Thus, we can expect northern tier states to be warm and relatively dry, the south having normal to cool temperatures and wet from southern California to the East Coast. In a La Niña event, the energy is concentrated in the western Pacific basin.

In this Hemisphere

For North America, La Niña brings a more variable northern jet stream and a northern storm track with occasional cold outbreaks. La Niña tends to bring warm and dry conditions to the south with cooler and wetter conditions to the north. Although the EN/LN cycle is less of a weather controller in summer, there is one important effect—El Niño summers tend to have fewer Atlantic hurricanes due to wind shear because of relatively strong westerly winds aloft in the tropics. Conversely, La Niña years see less wind shear and increased tropical cyclone activity.

You would think that because of its influence and possible major impact on winter weather, the EN/LN cycle would be a great forecasting tool for meteorologists. Yes, it’s often the basis of winter forecasts, but it’s not so simple. By closely monitoring ocean temperatures in the central and eastern Pacific, meteorologists can typically tell when one phase or the other is beginning, and because it takes months to achieve maximum strength, they can give advanced warning, but the EN/LN cycle is not a regular occurrence.

An El Niño event is not necessarily followed the next year by a La Niña. The return period on the cycle varies from two to seven years, and the strength of the actual event varies considerably. There are also other weather influences that can override the El Niño or La Niña effects, and these other factors can’t be forecasted months in advance.

Current State

The winter of 2015-16 saw the strongest El Niño on record and was the first El Niño since 2009-10. This was followed by weak La Niñas the next two winters. In 2018, fall saw tropical Pacific Ocean temperatures running above normal, and it appeared that an El Niño was developing, but it’s a weak one. The official winter forecast (Dec-Feb) reflects this with only the southeastern part of the country predicted to have near normal temperatures and the rest a bit warmer. Wet conditions are forecasted for the southern tier states, while the north is expected to be normal to dry.

You may wonder what causes the EN/LN cycle. Well, we don’t know. Does climate change affect the cycle? Probably, but it’s hard to prove. It’s speculated that the EN/LN cycle has been going on for thousands of years and, most likely, will continue for many thousands more.

By Ed Brotak, Southern Boating January 2019

Our Rising Seas: Coastal Resilience

Rising seas are more than a threat. They’re a reality.

It’s been a little more than a year since I first wrote about rising sea level and the problems it is causing. In this time, a considerable amount of data has come out on rising seas.

Unfortunately, most of it is not good news. A recent study of the Antarctic ice sheet concluded that the ice loss rate—which has amounted to 3 trillion tons in the last 25 years—as tripled in the past 10 years, adding to the rise in sea level. Another group of researchers noted that if the glaciers that hold back ice sheets on top of Antarctica and Greenland were to collapse, this could lead to extremely rapid rising seas around the world.

In this scenario, it’s predicted locations like South Florida could see a sea level increase of 10 to 30 feet by 2100. Another study on global mean sea level using satellite altimetry shows not only is sea level rising, but the rate of rise is too. This means that actual sea levels by 2100 could be twice as high as currently predicted using the observed rate of increase.

Significant Shifts

In an article published in July, a group of scientists compared future climate forecasts with past climates of a similar temperature. A warming of 1.5˚C (well below the 2˚C goal of the Paris Climate Agreement) could bring about “significant shifts in climate zones and the spatial distribution of land and ocean ecosystems.” The scientists said, “The changes we see today are much faster than anything encountered in Earth’s history. We can expect that sea level rise could become unstoppable for millennia.”

In my previous article, I noted that there has been a significant increase in “fair weather” flooding or flooding that occurs with non storm-related high tides. Although seas are rising everywhere, the amount of increase is not consistent around the world. The southeast coast of the U.S. has been particularly hard hit. A slowing of the Gulf Steam which transports water away from the East Coast and changes in atmospheric circulations seem to be the causes. In Miami, fair weather flooding events now occur 20 times per year. Charleston had 50 such events in 2016.

In a study released by the National Oceanographic and Atmospheric Administration (NOAA) in February, it was noted that the rate of such flooding was also increasing particularly along the southeast Atlantic coasts. Scientists concluded: “With continued sea level rise, high tide flood frequencies will continue to rapidly increase.”

Their forecast is even more startling. By 2100, even with conservative estimates of sea level, “high tide flooding will occur every other day or more.” Furthermore, with a higher sea level, “high tide flooding will become daily flooding.”

Coastal Resilience

The question is, “If we’re already at this point, can anything be done to protect our vulnerable coastlines?”

In 2007, the Coastal Resilience program was initiated by The Nature Conservancy (TNC), NOAA, the Association of State Floodplain Managers, several universities and private companies, and various international organizations. “Coastal Resilience” is defined by NOAA as “building the ability of a community to bounce back after hazardous events, such as hurricanes, coastal storms, and flooding, rather than reacting to impacts.

A community that is more informed and prepared will have a greater opportunity to rebound quickly from weather and climate-related events, including adapting to sea level rise.” From TNC’s viewpoint, “Coastal Resilience is a program to examine nature’s role in reducing coastal flood risk. The program integrates community engagement with maps. It’s delivered through a network of practitioners around the world supporting hazard mitigation, climate adaptation, and conservation planning.”

The first step is to define the problem. There are two aspects which must be considered: the threat and the threatened area. Threats include coastal storms, hurricanes, tsunamis, and high tide flooding. All are aggravated by the continuous sea level rise. The area threatened varies depending on the situation and coastal features.

What can be done to minimize flooding?

Coastal areas include natural habitats and man-made structures and infrastructure. Both must be considered when determining the risk and the ability to lower that risk. Solutions can also incorporate both. Nature has its own way of protecting coastal areas. Sand dunes can block damaging waves and, to a certain extent, the water level rises. Coastal wetlands and forests can similarly protect inhabited areas that are somewhat inland. Natural protection systems have been called Green Infrastructure. Where they’ve been damaged or destroyed, they can be brought back. Existing natural areas need to be protected.

In terms of human development, regulations, land use planning, building codes, and flood preparedness are tools. Structural features, such as sea walls, groins and breakwaters can be built. Natural habitats can be protected and maintained. Man can even mimic nature with artificial reefs, etc.

According to NOAA, “Decision-makers in coastal communities around the country need actionable information to make informed choices. The National Ocean Service provides a suite of services and expertise to help communities identify risks and vulnerabilities to apply sustainable solutions that increase resilience to the impacts of climate change, extreme weather and coastal inundation. This is about ensuring that coastal citizens, planners, emergency managers, and other decision-makers have the reliable information they need when they need it.”

See for Yourself

To help planners fully understand the critical issue they are actually facing, the Coastal Resilience Mapping Portal was developed. This web tool includes past and future flood risk models, FEMA Flood Zones, wetlands area, and land cover. By clicking on a map, users can also see what projects are already in progress.

One NOAA tool that is particularly striking is the “Sea Level Rise Viewer”. For selected coastal areas, you can see the predicted results of various amounts of sea level rise. If this isn’t enough, they have included recognizable landmarks and show how water will engulf them. To help communities plan for the future, NOAA Coastal Resilience Grants are available. NOAA will also provide educational materials and even courses on the subject.

By Ed Brotak, Southern Boating August 2018

Tangier Island

Tidewater Time Machine

Tangier Island is a remote, rustic and beautifully weathered area occupied by seafaring residents who speak a tongue stained with a dialect from their Old English ancestors and a surprising diversion from more typical and mainstream Chesapeake Bay cruising locales.

Lying nearly in the middle of Virginia’s emerald-green Chesapeake Bay waters, Tangier Island is a tiny sliver of marsh-peppered sand measuring just a mile wide by three miles long. It is so isolated that it can only be reached by boat.

The island’s residents stubbornly cling to every last inch of what’s left, as wind, waves and climate change steadily wash pieces of it away forever. Adversity and rugged beauty have left a charming patina on the island.

Visiting Tangier feels like going back in time. Folks crisscross the island using motorized and electric golf carts and scooters. Sometimes travel by outboard-powered skiff proves far more efficient than any other mode of transportation. You can’t buy liquor here, and the locals are quite conservative about outsiders consuming any bootleg booze they’ve brought along with them, as religious faith plays an important role in islanders’ lives. A doctor visits the local medical clinic once a month by helicopter, when weather permits.

Even electricity is piped in from the mainland. Still, Tangier’s residents relish their individuality and freedom. Visiting the island to soak in their culture and way of life—as well as to experience Tangier’s amazing scenery and wildlife— is well worth the pit stop.

Discovered more than 400 years ago by Captain John Smith, Pocomoke Indians occasionally inhabited the island before it was fully settled around 1686 by a Cornishman named John Crockett. Today, the last names of 450 permanent residents also include Pruitt, Thomas, Parks, and Evans. Many centuries of isolation have left locals with a heavy accent handed down by their Cornish ancestors, a sort of Old English similar to the thick brogue some Downeast North Carolina residents speak. Tangier’s population swells and recedes by a few hundred each day as tourists arrive and depart on ferry boats to get a look at the place and bolster the local economy in the process. Tourism aside, the island’s rhythm from April until November is dictated by crabbing. Today, some 70 watermen continue to work the plentiful waters around Tangier.

There are two limiting factors when it comes to cruising the area: your boat’s draft and your need for supplies. If your boat draws more than about six feet, dock in Crisfield, Maryland, and take the daily ferry to Tangier Island, about 15 miles across Tangier Sound. The Steven Thomas (800-863-2338) leaves Crisfield at 12:30PM daily and returns from Tangier, departing at 4PM sharp. Other ferry services include the Joyce Marie II (757-891-2505) from the eastern shore town of Onancock, Virginia, or the Chesapeake Breeze (804-453- 2628) from the western shore hamlet of Reedville, Virginia.

Other ferry services include the Joyce Marie II (757-891-2505) from the eastern shore town of Onancock, Virginia, or the Chesapeake Breeze (804-453- 2628) from the western shore hamlet of Reedville, Virginia.

Cruisers who want the full Tangier experience stay at Park’s Marina, the island’s sole marina, which has 25 slips and showers for slip holders but no pump-out. Fuel is available from two fuel docks on Tangier’s main watery thoroughfare.

There’s a general store and a few restaurants on Tangier but very little additional supplies, sundries or engine, and mechanical parts. There are, however, two motels and a handful of bed and breakfasts on the island. If you choose to visit by boat, there are two off-ramps from the main Chesapeake Bay channel into Tangier Island proper. The easiest approach is through what is identified as “Tangier Channel” on the chart but called “North Channel” by locals.

It lies on the west side of the island, starting at flashing green “1W” before making a dogleg at flashing green “3” and flashing red “4.” The other access is through the charted “Entrance Channel” to the east. This route requires rounding the Tangier Sound Light, keeping clear of green can “3,” and then pointing toward flashing green “1E” into the Entrance Channel. This passage has similar depths to Tangier Channel—around six feet at mean low water—but is considered somewhat more reliable because the ferry and mail/supply boats run it every day, helping to keep sediment from filling the channel in.

The first thing that will likely come into sight as you approach—by ferry or your own boat— are the many worn and weather-beaten crab shanties that line both sides of the thoroughfare. With dry land at a premium, watermen use these stilt-supported shanties as places to stow their crabbing and oystering gear and secure their boats. The two entrance channels eventually meet in the middle, forming a small harbor that is often the center of waterfront activity on the island. Small outboard-powered skiffs crisscross the harbor at a frenetic pace, interrupted only by the comings and goings of traditional Chesapeake deadrise workboats heading out to the crabbing grounds or returning home to sell their catch. Buyboats from the mainland visit the island daily to secure these catches and return them to shoreside processing facilities. Watching—and listening to the banter during the transfers—can be quite entertaining.

If you have an outboard-powered dinghy, poke in and out of Tangier’s interesting nooks and crannies. Start by motoring slowly along the waterfront where watermen at their crab shanties work on their nets and crab pots or tinker with the engines on their boats. The handful of shanties with water pouring from them are soft-shell crab shedding facilities.

Blue crabs grow by occasionally shedding their hard exoskeleton for a larger shell. These shedding facilities buy crabs scraped up or trapped by watermen from the local grass flats and then put them in pens until they shed. Once a crab discards its old shell, it must be immediately plucked from the water or the shell will quickly harden. This makes shedding crabs a 24/7 operation. Once you’ve had a soft-shell crab sandwich, you’ll realize the hard work is worth it.

You can also take your dinghy to some of the marsh islands north and east of Tangier. The Uppards, a collection of islands north of Tangier proper, is particularly fascinating. Once inhabited, they are now abandoned and actively being washed away leaving hints of civilization, including headstones and human bone fragments that lie in the wash zone scoured by the waves. Indians left items behind here, too. A careful eye can find an arrowhead or two in the sand on a walk around the shoreline. Port Isobel is an island just east of Tangier and owned by the Chesapeake Bay Foundation. They’re friendly to visitors, and the area is great for birdwatching.

No matter which marshy island you set foot on, biting black flies take painful chunks out of visitors not covered in insect repellent; you’ve been warned. Once you’re back ashore, walk around the island—or rent a golf cart—to take in the scenery. Don’t be surprised by the cemeteries in many of the homes’ front yards. Space is a premium on the island, so some families use their own land for laying relatives to rest. You’ll also see huge stacks of orange and yellow crab pots, beautiful old churches and homes with no lack of character and interesting style.

Visit the Tangier History Museum (16215 Main Ridge Road, 757-891-2374) for the local scoop, so to speak, and learn how the island has changed over the years. A trip to Tangier isn’t complete until you’ve sampled locally caught seafood that’s prepared in true Chesapeake style. Soft-shell crabs and crab cakes are a favorite on the island, and the folks at Fisherman’s Corner know how to prepare them just right.

Four Brothers Crab House and Ice Cream Deck is also a great place to grab a crab cake or soft-shell sandwich to go, but you should make it a point to get ice cream one evening and enjoy it on the deck outside the take-out window. Here, you can listen to the locals talk politics and engage in gossip with their unique and colorful accents. Lorraine’sSnack Bar is another joint serving great seafood sourced from local waters.

Visit Tangier while you can. Scientists estimate it may be overcome by water completely within 50 years, if the current rate of sea level rise continues. When you get there, you’ll discover a beautiful, rugged place populated by interesting folks who march to the beat of their own drummer, no matter what Mother Nature throws their way.

Cruiser Resources

DOCKAGE

Somers Cove Marina
715 Broadway, Crisfield, MD
(410) 968-0925

Park’s Marina
16070 Parks Marina Lane, Tangier, VA
(757) 891-2581

TANGIER RESTAURANTS

Fisherman’s Corner
4419 Long Bridge Road
(757) 891-2900

Four Brothers Crab House and Ice Cream Deck (also golf cart rental)
16128 Main Ridge Road
(757) 891-2999

Lorraine’s Snack Bar
(757) 891-2225

By Gary Reich Southern Boating June 2017

Are Acidifying Oceans Slowing Coral Disease?

Blackout Black Band

Could acidifying oceans actually slow down coral disease?

Coral reefs face intensifying struggles as greenhouse gases warm and acidify the ocean, but new research suggests a potential silver lining: Some coral diseases might also dwindle amid environmental change. A controlled lab study led by Mote Marine Laboratory and published in the journal

A controlled lab study led by Mote Marine Laboratory and published in the journal PLOS ONE revealed that black band disease was less deadly to mountainous star coral (Orbicella faveolata) as water acidiﬁed, or decreased in pH. Scientists from Mote and the University of South Carolina, and students from the University of Rhode Island, University of New Hampshire, University of Hawaii, and Unity College in Maine conducted the research with funding from the Dart Foundation and the Protect Our Reefs grants program supported by sales of the Protect Our Reefs specialty license plate. Student contributions were backed by the National Science Foundation (NSF) Research Experiences for Undergraduates program and Mote College Internship Scholarships.

Scientists from Mote and the University of South Carolina, and students from the University of Rhode Island, University of New Hampshire, University of Hawaii, and Unity College in Maine conducted the research with funding from the Dart Foundation and the Protect Our Reefs grants program supported by sales of the Protect Our Reefs specialty license plate. Student contributions were backed by the National Science Foundation (NSF) Research Experiences for Undergraduates program and Mote College Internship Scholarships.

The ocean’s pH is decreasing through the process of ocean acidiﬁ cation (OA) driven by excess carbon dioxide, the same greenhouse gas that’s triggering temperature increases worldwide. OA may weaken or dissolve corals’ hard skeletons and bring on other changes in multiple marine species. Warming water stresses corals, causing them to lose the vital algae in their tissues. Coral diseases, another major threat, may worsen in stressed corals, but few studies have examined how these conditions could change amid low pH levels expected with OA.

The new study is the ﬁrst to examine how low pH water affects black band—a fast-progressing, often deadly, worldwide coral disease affecting at least 42 coral species in the Caribbean. Black band, a variable group of multiple bacteria species, forms a dark circle that spreads across a coral and kills it. Under attack is mountainous star coral, a major contributor to the reef system of the Florida Keys and listed as threatened under the U.S. Endangered Species Act.

“Mountainous star coral only grows a couple of millimeters a year, and black band can kill a 100-year-old coral within weeks,” said Dr. Erinn Muller, lead author and manager of Mote’s Coral Health and Disease Research Program.

At a very small scale, black band produces a lower pH environment than its surroundings—localized acidiﬁ cation. “In the lab, we thought that exposing an infected coral to acidiﬁ ed water would accelerate the virulence of this disease, but to our surprise, the opposite happened,” Muller said.

During 2013 lab work at Mote’s Summerland Key campus, the researchers inoculated 32 mountainous star coral fragments with black band disease. Some were placed in tanks with temperature and pH similar to present-day ocean water, while others were put into tanks with elevated temperature, lowered pH or both. They used year-2100 projections from the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.

“These experimental studies in the lab are extremely important; they give us a glimpse into the potential future for our reefs,” said Mote’s Ocean Acidiﬁ cation Research Program manager Dr. Emily Hall, who oversees research in Mote’s Ocean Acidiﬁcation Flow-through Experimental Raceway Unit on Summerland Key, which was established due to an NSF grant. “With ocean acidiﬁcation, not every organism is affected the same way. It’s important for managers of marine protected areas to know how the impacts might vary.”

The researchers carefully monitored the water conditions and photographed and measured the coverage of black band for 16 days. By then, some coral fragments had perished completely from the disease. The team sampled black band bacteria and the corals’ natural resident bacteria—some of which contribute to the coral immune system—and sequenced their 16S rRNA gene, which helps classify bacteria into scientiﬁc categories. Their analysis revealed a surprise.

“Though warmer temperatures didn’t signiﬁcantly affect the progression of black band disease in this time period, the low pH treatment did—it slowed the progression rate of the disease by 25 percent,” Muller said. “It took us awhile to believe it.” Skeptical, Muller and her colleagues ran similar tests with other coral species apart from the mountainous star coral in the current study. The mountainous star coral showed the clearest trend, but data from other species suggested similar patterns.

How might acidiﬁcation slow down black band disease?
“Black band disease has a very distinct consortium of microbes, and it seems that lowered pH affected different microbes in different ways,” said study partner Dr. Kim Ritchie, associate professor at the University of South Carolina at Beaufort. “The abundance of one signiﬁ cant member of the consortium went down.” Speciﬁcally, acidiﬁed water reduced the abundance of Oscillatoriophycidae, a class of cyanobacteria that often dominates black band disease. These bacteria carry pigments that give the disease its distinct color. Though these bacteria live in the already-acidiﬁed environment of black band, past studies by others suggest that cyanobacteria can decline if the water becomes acidiﬁed beyond their tolerance limits.

“There were also shifts in the corals’ own microbial community, but none that explained the change in the disease. What happened in the black band itself, a reduction in the main contributor to the disease consortium was likely a better explanation,” Muller said. “One of our next steps is to study how low pH inﬂuences the very small scale conditions in the microenvironment of black band disease as the outside environment changes.”

By Hayley Rutger, Mote Marine Laboratory for Southern Boating August 2017

Seagrass Struggling Years After Heatwave

Seagrass Struggling to Revive

Massive seagrass beds in Western Australia’s Shark Bay—a UNESCO World Heritage Site—haven’t recovered much from the devastating heat wave of 2011, according to a new study demonstrating how certain vital ecosystems may change drastically in a warming climate.

The peer-reviewed research, recently published in Marine Ecology Progress Series, was led by Dr. Rob Nowicki, a Mote Marine Laboratory postdoctoral research fellow, who conducted the fieldwork while earning his doctorate from Florida International University (FIU). Dr. Michael Heithaus, dean of FIU’s College of Arts & Sciences, and colleagues from multiple institutions have examined Shark Bay’s ecosystem for more than 20 years. The current study included partners from FIU, Deakin University in Australia and Nova Southeastern University in Fort Lauderdale, Florida.

Shark Bay earned its World Heritage status, in part, because of its 1,853 square miles of seagrass beds, which UNESCO’s website calls the “richest in the world.” This vast, subtropical ecosystem hosts thousands of large sharks, other fish, sea turtles, bottlenose dolphins, and a critical population of dugongs, plant-eating mammals related to manatees.

“We were studying a relatively pristine ecosystem, but in summer 2011, we had the hottest water temperatures on record at the time, and we saw 70 to 90 percent losses of seagrasses at our study sites; no one expected it to be that bad,” Nowicki said. “After our colleagues documented the losses, we wanted to know how much the ecosystem might recover over a few years. If you take a punch and get up quickly, you’re ready for the next punch. But our study has suggested this system took a punch, and in the short term, it has not gotten back up.”

The researchers surveyed 63 sites in Shark Bay four times between 2012 and 2014 to assess seagrass recovery and changes. Before the heat wave, many sites were dominated by the temperate seagrass known as “wireweed” (Amphibolis antarctica), whose dense and tall thickets provide ample food and shelter for numerous species. The heat wave drastically thinned many wireweed beds, and in many places their
rhizomes (underground stems) blackened and died, leaving bare sand.

The new study showed that surviving A. antarctica beds appeared stable but didn’t reclaim much turf. Instead, the tropical seagrass Halodule uninervis, a close relative of the shoalgrass native to Florida, began filling the gaps. H. uninervis was spotted at 2 percent of sites in 2012 but had expanded to almost 30 percent of them by 2014.

“The seagrass hit hard was the most common species—and was dense like a mini forest,” said Heithaus, doctoral advisor to Nowicki and co-author of the study. “Losing that cover is really huge; it’s like going from a bushland in Africa to a well-mowed lawn.”

The loss of that much structure has consequences. “After the die-off, we also saw water clarity go down a ton,” Nowicki said. Fewer seagrasses were available to trap sediments, and decaying seagrass may have nourished a bloom of microscopic algae observed in 2014. Study authors say these ramifications aren’t surprising given the valuable ecosystem services healthy seagrass beds provide.

A scientist measures the growth of seagrass that is in the process of recovery from a 2011 heat wave.

Seagrass beds stabilize sediments, preventing erosion and clarifying water. More seagrass biomass can store more carbon dioxide, decreasing its availability to harm ecosystems through climate change and ocean acidification. Dense seagrass beds are also critical for economically important fisheries. Seagrass meadows are valued at $1.9 trillion worldwide just for their role in cycling nutrients, according to a 2009 study by others in Proceedings of the National Academy of Sciences. However, major seagrass ecosystems around the world have declined by about 7 percent per year since 1990, reminiscent of the drop in coral reefs and other vital ecosystems.

In Shark Bay, beds of slow-growing A. antarctica seagrass may struggle to recover further, the study suggests. Shark Bay, located where temperate and tropical ecosystems overlap, is among the warmest areas that A. antarctica can occupy, and hotter temperatures are predicted to become more common with climate change.

Because of its temperate-tropical overlap, Shark Bay has a diverse group of about 12 seagrass species—roughly twice as many as the entire state of Florida. Its diversity survives, along with other key features that helped earn the site’s World Heritage status.

It’s imperative to continue investigating how the recent loss of some seagrass, a basis of the marine food web, will affect plant-eating animals and their predators in Shark Bay.

Some take-home messages are clear: It’s critical to monitor ecosystems well after a disturbance; they’re not guaranteed to bounce back. “It shows the importance of these long-term, comprehensive, ecosystem-level studies,” said Heithaus, referring to team efforts to examine Shark Bay. “If we hadn’t been doing this since 1997, we wouldn’t have had the baseline data to know that the declines were a big deal.”

Also, if relatively pristine seagrass beds of Shark Bay are vulnerable to extreme weather, then it’s unclear how seagrass beds damaged by human activity will fare in the coming decades. This seagrass struggling is an indicator that humans need to be aware of these occurances.

Nowicki said that minimizing local stressors, such as nutrient pollution from fertilizer runoff into bays and estuaries, may give seagrasses better odds amid climate change and other global stressors. “If Shark Bay had poorer water quality, we might have lost a lot more.”

By Mote Marine Laboratory and Aquarium for Southern Boating Magazine June 2017