New Study Reveals Whales as Marine Ecosystem Engineers

Baleen and sperm whales, known collectively as the great whales, include the largest animals in the history of life on Earth.

Though large in size, whales have long been considered too rare to make much of a difference in the ocean, and the focus of much marine ecological research has been on smaller organisms, such as algae and planktonic animals. While these small organisms are essential to life in the sea, they are not the whole story. As great whales recover from centuries of overhunting, scientists are beginning to appreciate their roles as ecosystem engineers of the ocean.

A recent synthesis, published in Frontiers in Ecology and the Environment, evaluates decades of research on the ecological role of great whales. The authors, led by Joe Roman at the University of Vermont, suggest that the influence of these animals has been substantially undervalued because, until now, scientists have underestimated the degree to which the decline in whale population has altered marine ecosystems.

Commercial whaling dramatically reduced the abundance of great whales—by at least 66 percent and perhaps as high as 90 percent, according to some estimates—but recovery is possible, and potentially critical for ocean resiliency.

Among their many ecological functions, whales recycle nutrients and enhance primary productivity, locally and on a regional scale. Whales mix the water column, and after feeding at depth, release surface plumes of fecal material. This "whale pump" supplies iron and nitrogen—essentially fertilizers—to primary producers in the surface ocean. Further, the migrations of baleen whales between highly productive, high-latitude feeding and low-latitude calving grounds are among the longest annual movements of mammals. By fasting in these winter calving grounds near the equator, humpback whales, for example, release nitrogen in the form of urea into comparatively nutrient-poor areas—transporting nutrients nearly 10,000 kilometers on the "great whale conveyor belt."

Sometimes, commercial fishermen have seen whales as competition. But this new paper summarizes a strong body of evidence that indicates the opposite can be true: whale recovery "could lead to higher rates of productivity in locations where whales aggregate to feed and give birth," supporting more robust fisheries.

Whales, as one of the longer-lived species in marine systems, can ease the impact of perturbations inclimate, predation and productivity. The continued recovery of great whales may help buffer marine ecosystems from destabilizing stresses and could lead to higher rates of productivity in locations where whales aggregate to feed and give birth.

And when they die, many whale carcasses sink to dark depths of the ocean—delivering massive pulses of organic material to a realm that is typically nutrient and energy impoverished. A 40-ton gray whale, for example, provides more than 2,000 times the background carbon flux that would typically rain down on the area underlying the carcass in an entire year.

"Whales appear to harbor a specialized suite of animals in the deep sea, with many species requiring whale falls to complete their life cycles and persist in the ocean," said Craig Smith, co-author and Oceanography Professor at the University of Hawai‘i at Mānoa. "When whales were removed from the ocean by whalers, these whale-fall specialists lost their essential habitat." More

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I question if it would be possible for humans to work with marine mamals and other sea creatures to 'manage' the oceans for the benefit of the marine environment, the inhabitants of the oceans as well as the living beings on the planet. It would certainly be beneficial to all concerned and would possible go some way towards mitigating climate change. Editor

 

© 2014

Pacific islands look for model to combat changes due to global warming

With islands and atolls scattered across the ocean, the small Pacific island states are among those most exposed to the effects of global warming: increasing acidity and rising sea level, more frequent natural disasters and damage to coral reefs.

These micro-states, home to about 10 million people, are already paying for the environmental irresponsibility of the great powers.

"Pacific islands are the victims of industrial countries unable to control their carbon dioxide emissions. The truth of the matter is that we have no option but to accept this and adapt," says Dr Jimmie Rodgers, the head of the Secretariat of the Pacific Community (SPC), a regional development organisation. At the initiative of France's Research on Development Institute (IRD) and New Caledonia University, 30 or so scientists from the Pacific basin spent a week at the end of April discussing the design of asustainable development model suited to local conditions – in particular, pressure from the climate on ways of life that reach back several millennia.

In a study published by the journal Nature Climate Change, the SPC and IRD draw attention to the considerable impact of global warming on food security on these islands. Fish stocks, the main source of protein for islanders and the basis for development, will be particularly affected. Currently about 1m tonnes of tuna and tuna-like fishes are caught every year in the region.

For the Kiribati group of islands, fishing accounts for 40% of GDP, whereas on the Marshall Islands fisheries and fish processing represent a quarter of overall revenue. "The rising temperature of surface waters, which is greater in the western part of the ocean basin, will encourage tuna to migrate east towards Polynesia," says Johann Bell, principal fisheries scientist at SPC and one of the authors of the study.

Melanesian countries, such as Papua New Guinea or the Solomon Islands, will suffer most. "PNG has a large canning industry, but in a few decades it will have to import tuna to keep it running," Bell adds. "Fortunately it can count on favourable international agreements to buy [fish] wherever it likes, with low customs duty." But the disappearance of the tuna shoals could mean major financial losses for smaller economies such as Tuvalu or Kiribati.

The effects for coastal fisheries are likely to be even more dramatic, due to damage to the coral reefs. The population density of live reefs is expected to drop from 40% at present, for the Pacific as a whole, to 10% or 20% by 2050, the scientists explain. The decrease in the fish stocks in the lagoons coincides with high population growth, particularly inMelanesia.

With an increase in rainfall, the SPC is advocating the development of fish farms and freshwater fisheries. On Fiji, Vanuatu and Samoa, farms have recently started raising Nile tilapia, an alien species. To reduce pressure on the reefs and allow coastal residents to catch tuna, there are also plans to build floating pontoons to attract the fish.

On land, life must adapt to the changing conditions too. On Fiji, the Centre for Pacific Crops and Trees has set up a department to focus on adapting staple crops.

"Climate change brings new constraints for crops, which are subject to unpredictable ecological pressures such as drought, higher salt concentrations, extreme temperatures and erosion," a representative explains. Thousands of varieties of manioc, taro, sweet potato and banana have been screened in order to offer farmers new, more robust varieties. "We are promoting these seeds," says Henry Puna, prime minister of the Cook Islands (population 12,200), which have been hard-hit by coastal erosion. More

 

Taking Stock: World Fish Catch Falls to 90 Million Tons in 2012

The U.N. Food and Agriculture Organization (FAO) projects that the world’s wild fish harvest will fall to 90 million tons in 2012, down 2 percent from 2011. This is close to 4 percent below the all-time peak haul of nearly 94 million tons in 1996.

The wild fish catch per person has dropped even more dramatically, from 17 kilograms (37.5 pounds) per person at its height in 1988 to 13 kilograms in 2012—a 37-year low. While wild fish harvests have flattened out during this time, the output from fish farming has soared from 24 million tons in the mid-1990s to a projected 67 million tons in 2012.

Over the last several decades, as demand for fish and shellfish for food, feed, and other products rose dramatically, fishing operations have used increasingly sophisticated technologies—such as on-vessel refrigeration and processing facilities, spotter planes, and GPS satellites. Industrial fishing fleets initially targeted the northern hemisphere’s coastal fish stocks, then as stocks were depleted they expanded progressively southward on average close to one degree of latitude annually since 1950. The fastest expansion was during the 1980s and early 1990s. Thereafter, the only frontiers remaining were the high seas, the hard-to-reach waters near Antarctica and in the Arctic, and the depths of the oceans.

The escalating pursuit of fish—now with gross revenue exceeding $80 billion per year—has had heavy ecological consequences, including the alteration of marine food webs via a massive reduction in the populations of larger, longer-lived predatory fish such as tunas, cods, and marlins. Unselective fishing gear, including longlines and bottom-scraping trawls, kill large numbers of non-target animals like sea turtles, sharks, and corals.

As of 2009, some 57 percent of the oceanic fish stocks evaluated by FAO are “fully exploited,” with harvest levels at or near what fisheries scientists call maximum sustainable yield (MSY). If we think of a fish stock as a savings account, fishing at MSY is theoretically similar to withdrawing only the accrued interest, avoiding dipping into the principal.

Some 30 percent of stocks are “overexploited”—they have been fished beyond MSY and require strong management intervention in order to rebuild. The share of stocks in this category has tripled since the mid-1970s. A well-known example of this is the Newfoundland cod fishery that collapsed in the early 1990s and has yet to recover.

This leaves just 13 percent of oceanic fish stocks in the “non-fully exploited” category, down from 40 percent in 1974. Unfortunately, these remaining stocks tend to have very limited potential for safely increasing the catch.

These FAO figures describe 395 fisheries that account for some 70 percent of the global catch. Included are the small minority that have undergone the time-consuming and expensive process of formal scientific stock assessment, with the remainder being "unassessed" fisheries. There are thousands more unassessed fisheries, however, that are absent from the FAO analysis. In a 2012 Science article, Christopher Costello and colleagues published the first attempt to characterize all of the world’s unassessed fisheries. The authors report that 64 percent of them were overexploited as of 2009.

The top 10 fished species represent roughly one quarter of the world catch. Nearly all of the stocks of these species are considered fully exploited (most of these fish have more than one geographically distinct stock), including both of the major stocks of Peruvian anchovy, the world's leading wild-caught fish. Stocks that are overexploited and in need of rebuilding include largehead hairtail—a ribbon-like predator caught mainly by Chinese ships—in its main fishing grounds in the Northwest Pacific. (See data.)

Despite the unsustainable nature of current harvest levels, countries continue to subsidize fishing fleets in ways that encourage even higher catches. Governments around the world spend an estimated $16 billion annually on increasing fleet size and fish-catching ability, including $4 billion for fuel subsidies. Industrial countries spend some $10 billion of that total. More than $2 billion is spent by China, whose 15-million-ton catch is nearly triple that of the next closest country, Indonesia. More