Phenology and physiology
Changes to the timing of life cycle events (phenology)
Phenology is a term used to describe the timing of life cycle events such as spawning or migrations. Often these cycles and events have evolved under very specific conditions and are triggered by changes in the natural environment, such as day length or seasonal temperature variations.
Ecosystems are very complex and there are many different interactions (predator/prey, competition for shelter and food) and links between species. We need to develop a better understanding of how climate change is infuencing the timing (phenology) of ecological events s changing interactions between species, and how adaptive species and their broader ecosystems are to these changes.
Phenological changes are difficult to detect in marine species and little information exists in Australia.
- The egg laying dates of Little Penguins in Bass Strait are earlier in warmer years
- The timing of peak rock lobster puerulus settlement has shifted to later in the year (from July to October).
A five centimetre southern rock lobster. Puerulus larvae spend most of the time swimming in the ocean before settling onto rocky seafloor and turning into a young lobster (Image: TAFI).
Physiological responses
However, some species may thrive under the new conditions and their physiological response may be to become more abundant or to grow faster. For example within the upper regions of the oceans all over the world are tiny plants and animals that can not be seen with the naked eye. This sea soup known as plankton can be subdivided into zooplankton (animals), and phytoplankton (plants). These tiny creatures are very susceptible to climatic changes and the nutrient levels within the waters they live and are likely to become so abundant under certain conditions that they can be seen floating on the water as a toxic ‘bloom’.
Noctiluca scintillans a plankton that survives by ingesting ready-made
organic matter in its environment rather than synthesizing its own energy as
plants do (Image: Anita Slotwinski).
There are documented cases in Tasmania in which dense 'red tides' of Noctiluca, a type of zooplankton, has bloomed in response to a combination of increased nutrient loads and warming waters. The changes to noctiluca and other zooplankton species are very important and the role of zooplankton in the environment is not to be underestimated. Scientists are predicting that zooplankton will play a vital role in climate change science by acting as 'indicator species' for climate change impacts. That is, zooplankton may just be the oceans early warning system that changes are occurring.
Noctiluca: Mostly restricted to temperate, subtropical and tropical coastal waters. This tiny species produces pinkish
coloured water when it blooms in Australian waters (Image: Marshall & Hallegraeff, UTAS)
Sources:
Hobday, A., T.A. Okey, E.S. Poloczanska, T.J. Kunz, and A.J. Richardson. (eds).(2006).
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Hallegraeff, G, Hosia, W, Knuckey R, Wilkinson C. (2008) Recent Range expansion of the
red-tide dinoflagellate Noctiluca scintillans in Australian Coastal Waters. IOC-UNESCO
Harmful Algae Newsletter 38:10-11.
Pecl G, Frusher S, Gardner C, Haward M, Hobday A, Jennings S, Nursey-Bray M, Punt A,
Revill H, van Putten I (2009). East coast, Tasmania – an assessment of climate change
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Change Coastal Vulnerability Assessment (NCVA). Report to the Department of Climate
Change, Australia. April 2009. www.climatechange.gov.au/publications/coastline/east-coast-rock-lobster.aspx
Poloczanska ES, Babcock RC, Butler A, Hobday AJ, Hoegh-Guldberg O, Kunz TJ, Matear R,
Milton D, Okey TA, Richardson AJ (2007) Climate change and Australian marine life.
Oceanography and Marine Biology Annual Review, 45, 409–480.
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