|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
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.
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.
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
|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
Dalhousie marine photos:
A strange and beautiful world