Swirling clouds of blue and green lit the Atlantic Ocean west of Ireland on June 2, 2006, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this image. The ocean is normally black in true-color, photo-like satellite images such as this one, but a large phytoplankton bloom lent the water its brilliant blue and green hues. Phytoplankton are microscopic plants that grow in the sunlit surface waters of the ocean. When enough of the plants grow in one place, the bloom can be seen from space.

Rising sea temperatures over 100 years is harming the tiny plant life that forms the base of the oceans' food chain as well as affecting the diversity of marine life, two new studies have found.

NASA  - - the US National Aeronautics and Space Administration  -- says that aside from colouring ocean waters, the tiny plant life, known as phytoplankton, play a large role in sustaining ocean ecosystems and in global climate. The tiny plants are the base of the marine food chain, and places where blooms are frequent tend to support a thriving marine population. Since the plants need nutrients like iron to grow, fertile waters are often near a continental shelf in areas where cool water from the ocean’s depths pushes to the surface. This upwelling water carries with it nutrients that had settled to the ocean floor; the nutrients allow the water to sustain large phytoplankton blooms.

Phytoplankton influence global climate by regulating gases in the atmosphere. Like all plants, phytoplankton absorb carbon dioxide and release oxygen as they grow. When the plants die, they sink to the ocean floor, carrying the absorbed carbon with them. Over the course of the Earth’s history, the oceans have become the primary sink for atmospheric carbon dioxide. Since carbon dioxide is a greenhouse gas (it traps heat at the Earth’s surface), the Earth would be a much warmer place without phytoplankton.

Researchers at Dalhousie University in Nova Scotia, have spearheaded a groundbreaking study examining marine biodiversity in the world’s oceans. Led by Derek Tittensor, the study examines an unprecedented 11,000 marine species ranging from microscopic plankton to the whales and sharks.

Scientists estimate that the oceans have warmed about half a degree Celsius on average over the past 100 years and the Dalhousie scientists used data obtained with a simple oceanography device known as a Secchi. The device has been used by scientists since the late 1800s, and is a disk lowered into the water to provide an estimate of water clarity and accordingly serves as a proxy measure of phytoplankton abundance.

By collating and analysing about half a million Secchi observations, plus other direct measurements of algae, the Dalhousie team estimated that phytoplankton levels fell by about 1% of the global average each year from 1899 onward. The data are more reliable for recent decades, translating into a 40% decline in algae since 1950.

The international project also includes Dal professors Camilo Mora, Heike Lotze, Daniel Ricard and Boris Worm, Edward Vanden Berghe from Rutgers University, and Walter Jetz from Yale University.

The Canadian Coast Guard Ship Hudson was home for 27 scientists during the month of July. From the ship, they sent down the ROPOS — remotely operated platform for ocean science — to the sea floor to collect photos, video and samples. An international crew of Canadian and Spanish biologists and geologists were able to see sealife and ecosystems never seen before.

By studying a broad range of species, both big and small, researchers were able to draw conclusions and map certain “hot spots” of diversity.

“Areas that we identified as hot spots had higher numbers of multiple species,” says Dr. Tittensor, postdoctoral fellow with Dalhousie’s Department of Biology. “Unfortunately, these areas also tend to be more vulnerable to outside influences such as commercial fishing, pollution and other types of habitat interference.”

The one thing that areas of marine biodiversity appear to have in common is temperature. Typically, areas that are hot spots of diversity have higher temperatures, but this is not always the case. The areas around the North and South Poles are home to many species of marine life such as seals, whales and multiple species of fish. Even so, Dr. Tittensor warns we should still be very concerned about the rising temperature of our world’s oceans.

“The main goal of this research was to be able to better inform conservation and management of the environment in regards to the ocean and marine life. By highlighting areas of marine biodiversity we can hopefully better manage them,” he notes. “This study will also be able to provide a baseline for future research. Forty or 50 years from now, researchers will be able to use this study as a baseline measurement and track changes in the marine environment.”

The study authors point out the diversity of life in the global ocean is severely threatened. A steady onslaught of exploitation, habitat alteration, pollution and climate change auger a menace to the very makeup of the oceans. The authors suggest that limiting ocean warming and other human impacts is key to secure these hotspots of marine biodiversity in future.

Another team of scientists, including Dr. Worm, mapped the diversity of marine life on a broad scale. They found that while coastal marine species showed greater diversity at the equator, the diversity of oceanic species peaked in the mid-latitudes. That's unlike terrestrial diversity, which largely peaks at the tropics.

The research findings are published in the July 28, 2010 edition of the scientific journal, Nature

Global patterns and predictors of marine biodiversity across taxa  in Nature.

Dalhousie marine photos: A strange and beautiful world