Australia’s south eastern coastline is home to an array of unique and fascinating marine life. These organisms have adapted and acclimatised to temperate (cold water) conditions. However, climate change modelling predicts that Australia’s surrounding oceans will warm by 1–2 ⁰C by 2070, with the south east coast of Australia expected to feel the greatest effects due to increased strength and penetration of the East Australian Current (EAC)(on right).
Fig.1 Changes in Sea Surface Temperature (SST) since 1880 for southern and eastern Australia (CSIRO). Notice in the graphs, that water temperatures start rising above the long-term average after about the 1960s (Image: CSIRO).
The EAC pushes warm water from the tropics, i.e. around the Great Barrier Reef, southward into the temperate waters found along the south eastern coast. This strength varies seasonally and annually (see below)-
Fig. 2 The above shows the south east coastline of Australia (images CSIRO). The warm water(red/orange) is being pushed down from the tropics by the EAC into the cooler, temperate water (green/blue)
As a consequence to this predicted increase in ocean temperatures, there is mounting evidence suggesting that the geographic range of tropical and temperature coastal fish species will shift to higher latitudes (in this case further South), in response to warming trends. For example, ongoing studies around a coastal town called Merimbula (37°S) have recorded over 50 species of tropical fish which are aided by the warmer water and stronger EAC during Summer/Autumn. It is only when the warm water recedes and cold water replaces it, do these tropical fish die. With the predicted changes, these tropical fish are expected to survive through winter and compete with temperate fish species.
In addition to this, structurally important and unique macroalgae (e.g. bull kelp Durvillea potatorum) are predicted to have dramatic temperate fish range shifts. Preferring temperate conditions, increased ocean temperatures are predicted to radically move macroalgae distribution poleward. Warm ocean temperatures influence the health of macroalgae, often leaving large populations vulnerable to disease and wave action. Macroalgae provides important habitats for a number of temperate fish and invertebrate species throughout their life cycles, with predicted poleward shifts, species that require macroalgae habitats will either adapt or follow macroalgae range shifts.
Acknowledging these predicted changes, community members are establishing a long term monitoring program to record any annual and seasonal changes in fish diversity and macroalgae health. This would also include recording sea surface temperature.
1. Establish a monitoring programme that will build valuable data, recording biodiversity and changes over time
2. Monitor annual and seasonal changes in fish and invertebrate diversity and macroalgae health
3. Create and maintain an ongoing training program that improves interested community members knowledge about local marine life and improve their identification skills
4. Create an identification/education guide of the target fish and invertebrate diversity and health indicators on macroalgae.
5. Establish frequent monitoring of nominated sites and expand the number of survey sites over time
6. Encourage university involvement and/or grants
At this stage there are two methods to record fish diversity and macroalgae health.
1) Timed snorkel: using a recording template (that will have a list of key fish), participants will note down any fish species they observed and an estimated abundance. They will also note down any macroalgae discolouration.
2) Video footage: working with local fisheries, underwater video footage of offshore habitats (e.g. urchin barrens, rocky reefs) has been made available to the community working group. Analysis TBC
1) What data should we be aiming to record;
- Species wise: Should we aim to create a total species list and record as much of the biodiversity as possible OR create a targeted species list that aims to record indicator species of fish, invertebrates and macroalgae?
- Health: What is the best way to record the health of macroalgae?
- Abiotic parameters: we have access to temperature data loggers, but what other parameters should we look to record? E.g. depth, water clarity, tide, swell height etc
New to working with underwater video footage has created a few questions:
2) What would be the best way to utilise the video footage ? Footage shows macroalgae and fish species inhabiting habitats at different depths. (NOTE: original thoughts was to take snapshots of the footage and overlay randomised dots/points over the image. Dots/points that are over macroalgae would be highlighted and those that aren’t over macroalgae would be left alone)
3) Is there an online tool or free software to analyse video footage?
4) What would be the best way to standardise video analysis? Note: video footage will be from the same sites taken at different times of the year.