The weather at the moment has been ridiculously calm in the morning. This is normal for August. Winter is a time of generally light northerly winds and it’s the chance to see some wonderful ocean features in our bay. Here I want to explain a bit about what I was seeing today when I spent a few minutes scanning with binoculars off Red Bluff. What is interesting is how much you can see, hear and even smell from this location, that gives a clue as to the powerful influence our bay’s animals are having on the ecosystemHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More.
Here are 10 important ways bayside dolphins, seals & penguins help our lives. I listed these while I was watching. Oh, and a Peregrine Falcon flew over too! Don’t see those too often along this coastline.
I have recently downloaded the Sentinel-2 satellite data for this area. During that 2-3 days, the low winds meant the Yarra plume didn’t extend as far south. In the image below, the pale patches are fingers of freshwater extending south, alternating with parallel lines of saltier water. These are the stripes you can see in the picture above.
1. Current Lines
The pale patches of water you can see are current lines. At the time I was observing, the wind was lightly from the south. The calmer patches are where water was drifing north. It flattened out because the waves and sea were flowing in the same direction. The slightly rougher patches were water from the north and this is generally less saline because it comes from the Yarra. About ten minutes earlier, this pattern was reversed as the wind was coming from the north – it changes when the wind alters direction.
These current lines are the boundaries between layers of water. Some animals prefer the saltier water emanating from the centre of the bay and others like the more freshwater habitat. But it’s mostly along the boundaries where animals feed. Because this is where planktonA soup of micro-organisms. Usually refers to all the zooplankton and algae in the ocean but can also be used to describe tiny insects in the atmosphere (see aerial plankton). More gets concentrated. Right now is the major plankton growth period. Cold water and sunlight is vital.
2. Pied Cormorants
Dozens of Pied Cormorants were rafting in this area. During winter, this species breeds in Port Phillip Bay, mostly in Werribee. I suspect that Bayside’s coastal areas are essential feeding locations. The birds come here to dine on baitfish before regularly returning to their colony to feed young which would have only just hatched. Seabirds are considered to be critical for nutrient transfer between land and sea. Much of our coastal productivityThe power of an ecosystem to process energy. The most productive ecosystems have reached a steady stable-state with maximum entropy production. That’s to say, the number of species has reached an optimum and the functions they fulfil, have translated free surplus energy into nutrients that is either stored inside plants and animals, or is entrained within the biological cycles that More would be built around this annual seabird movement.
3. Australian Fur Seal
A big male Australian Fur Seal was feeding over the shallow reefs in this location. Other seals were ‘jug-handling’ further out, which is where they raise their flippers and use them to gather sunlight and warm up. These animals were scattered along the current lines much further out, in areas like B, G and H. It’s wonderful to see large marine mammals thriving in our near coastal waters. It’s a sign that the ecosystem is still in good health.
4. Cerberus Cormorant Roost
As the wind shifted south, you could smell the guano from this site, even from 300 metres away. Seabird colonies are the single biggest point source of ammonia on Earth. On days like today, this mixes with chemicals created by surface algae, creating sulphuric acid droplets. These are incredibly powerful cloud seeding mechanisms. In the Arctic, seabird colonies are thought to influence weather patterns at a continental scale. These birds will almost certainly be having a big effect locally. Perhaps, reducing disturbance to the remaining birds in summer, might also help amplifyAmplification (of nutrients and energy). Animals consume plants and other animals and in doing so, reintroduce important energy-containing nutrients back into the environment, at even higher concentrations and in patches. Amplification of energy is driven by migration and happens at every scale, from insects moving daily in and out of your vegetable patch, to African wildebeest herds and the seasonal More rainfall around the coast.
5. Bottlenose (Burranan) Dolphins
A small pod of dolpins was feeding in a patch just offshore. Wherever there are dolphins, there are usually seabirds. Silver Gulls, Crested Terns, another fur seal and no doubt many salmon, were present. The interaction of species creates systems-level impact on nutrientEnergy and nutrients are the same thing. Plants capture energy from the Sun and store it in chemicals, via the process of photosynthesis. The excess greenery and waste that plants create, contain chemicals that animals can eat, in order to build their own bodies and reproduce. When a chemical is used this way, we call it a nutrient. As we More processes. The dolphins the salmon distribution, which influence the baitfish distribution. This sets up the dynamic that enables the whole nutrientA substance that contains the raw materials for life. At a chemical level, these are contained inside compounds that are absorbed into the body and essential energy-containing molecules are extracted, so that energy can be transformed into other chemical processes that use the energy for living. More process to flourish. Without full support from top to bottom, we would not have such a healthy ecosystem.
6. Hoary-headed Grebe
During winter, huge numbers of Hoary-headed Grebes enter the bay from inland areas. They feed along the nearshore areas in and among the seagrass. During the winter months there is relatively little competition for prey here but they are also more tolerant of freshwater.
The majority of our coastline is inundated with a surface layer of freshwater that is continuously topped up by storm water drains. Some freshwater input is vital but it’s possible that increasing storm intensity and urbanisation is threatening some of our bay’s traditionally marine coastal species. It also results in huge amounts of dead seaweed and seagrass – which is currently piled up along the shore in some of the bays. Rebalancing the system might mean addressing freshwater as a pollutant.
7. Little Penguins
During the winter months, the majority of the adult penguins from Phillip Island enter the bay. The bay’s penguin population increases ten-fold, adding to the local population from St Kilda.
Within the areas of calm water (which in this case are the more saline areas pictured), the penguins were floating in rafts of between 6-10 individuals. They feed cooperatively, diving at the same time, presumably to herd the fish.
Being visual predators, they depend on good water quality. When underwater visibility declines even slightly, they might struggle to find food. The fish, meanwhile, prefer to be in slightly murkier water where they can hide. The Penguins swim along the current edges looking for baitfish to chase into clearer water and ambush.
8. Fishing boat and salmon
A fishing boat races out towards Australian Salmon. These are attacking baitfish, creating a mellee of seabird activity. The salmon are really vocal. When you snorkel with them, you can hear the shoal approaching with their clicks and grunts. Much of the underwater world runs on sound, not vision. Salmon are particularly sensitive to noise and the moment the boat thrusts its engines, the entire feeding frenzy dissipates. You can literally see the effect of underwater noise happening on the surface.
9. Australasian Gannets
Australasian Gannets are a common sight in winter. Overall, the bay’s circulation changes and this pushes nutrient rich water from the centre of the bay towards the bayside coastline. In the figure below (winter) you can see how there is a boundary between two currents running parallel to the bayside coastline.
It’s along this front, a little bit offshore, that there are constantly skeins of Australasian Gannets. They plunge headlong into the sea to catch fish. Most species are feeding on sardines, which are very nutrient rich.
Figure 1: OceanographyThe study of the physical, chemical and biological properties of the ocean. More of Port Phillip Bay. Winter (left / top) with predominant northerly winds; and summer (right / bottom) with predominant southwesterly winds and sea breezes.
10 Overall impact
The combination of all these factors, driven by animals, amounts to an immense amount of nutrient transfer(of nutrients) the thing that sets animals apart from plants, is that they can move. Some of the biggest migrations on Earth every day, are the movement of insects like caterpillars, from the stem of a plant to a leaf and back, before turning into butterflies and transferring the energy elsewhere. Large-scale migration of grazing animals and migratory songbirds moves More, amplication and concentration. It’s the driving force behind our bay’s health and it happens mostly in winter.
This area is quite remarkable, especially given its proximity to a major city. It’s a spot where you can observe powerful natural processes that establish the conditions for our whole summer. It’s happening all of the time and to maintain these values all we need to do, is ensure we stay aware of its importance and do what we can to preserve it.
