Great news from OZ REEF Marine Park this month, the pair of Valenciennea puellaris, Orange Spotted Goby, have spawned and hatched fry. There is also a feature article on an Envrionment Survey conducted on Port Phillip Bay.

Editorial

Welcome to the 13^th issue of OZ REEF Press :-) Yes, you have read correctly, this 13^th. Bummer, I missed the celebration of 12 months of publication, oh well, 13 will do fine. A lot of things have happened in that time too. I am sorry if you are after a rehash here, but you will just have to go back and read all the back issue, (I have a terrible memory ;-)) Anyway, what the also means is that OZ REEF Marine Park (the site) is 14 months old! I wonder if there is anyone out there that has read each single edition as I have put it online ... hmm if there is anyone out there that has done that, then I would love to hear from you. (I really want to ask why you keep coming back ;-) )

OK, enough rambling, time for some really cool news :-) My pair of Valenciennea puellaris, orange spotted gobies have decided that they love OZ REEF Marine Park that they would like to bring up their children there. That's correct, they have decided to SPAWN. As you should see by this emphasis, I am over the moon about this. This is mainly due to the fact that I have not heard from any source yet that they have spawned previous in captivity, though it is likely that I am yet to talk to the right people, and I must be doing something very well :-)

It all happened about 2 weeks ago. The gobies had been making a real mess of the tank for about 2 weeks, piling as much sand as they could over their burrow. Also the female disappered for 4 days at the start of this period, and was much more secretive after this. Then on Sunday morning at 10am I was walking past the OZ REEF and noticed that the Chromis viridis, Green Chromis, school were running around the tank frantically gulping something in. This seemed very strange as they had not been fed yet, and that is what it looked like they were doing. Apon closer inspection of the Park, I noticed that the water was full of larvae of some type. To stop the larvae from being consumed the lights were turned off, which immediately made the Chromis disappear in to the reef structure and stopped their feeding frenzy. I also turned off all the pumps, circulation and return. Then with a torch I looked all through the tank. There were literally thousands of larvae swimming around the tank, all about 2.5mm long. They were moving in short bursts about 2 body lengths long with a quick twitch of the body. These look very much like a very small fish, and from the tapered shape determine that they must be gobies. Small dark spots were visible on the head, obviously eyes.

Remembering that most fry are attached to light, I turned a light onto the base of the tank, and within 10 minutes that region was swarming with thousands of fry. It was just incredible. I syphoned a considerable amount of them out into a bucket, then tipped the bucket contents through a couple of breeding traps that I attached to the side of the tank. That was the only place I had to put them, no spare tanks at all. I rushed off to the store to find something to feed them, to started a green water culture, hatching brine shrimp etc, but they were all dead within 3 hours of the discovery. It is most likely that they starved, they had no yolk at all, and had no food supply.

The reason for them being released in the morning, as this is the worst time for larvae to be released as there is heaps of preditors around, and having no yolk, I believe is that they were trapped in gobies burrow overnight. Gobies typically plug their burrow overnight as they 'sleep'. The eggs hatched after the 'door' had been closed and were therefore trapped until the morning when the adults 'arose'. This I suppose is lucky in one respect, as if they had not been trapped overnight I would not have seen them as they would have been all consumer overnight and chewed up in the circulation pumps. Considering this, and the pre-spawning behavior, it is highly likely that they have done this before as the sand piling over there burrow has also be observed previously. Well, anyway I hope to be prepaired for the next time.

Currently are in the planning stages for a fry tank to hopefully keep and raise the goby fry in. (I managed to get another tank out of my fiance as until recently I have been limited to two tank. I mentioned that I was about to return the freshwater stock to the store so that I could convert it to a fry tank. That did not go down well ;-), how could I get rid of the nicest tank and those two beautiful angelfish? So the only alternative is to get another tank.) I plan to use a small tank, about 60cm long, partion off one end of the tank to put the filtration in. Above this partion will be an overflow, comprising of floss filter matting over the top of eggcrate, to allow the water to the filtration devices and not the fry. Within the filtration compartment will be a Rio 600 powerhead to pump the water back into the tank, the output will be controllable so that too stronger currents are not created. There will also be a small air operated skimmer, and a place to put some chemical media if the need arises. For lighting will only use a single normal output fluorescent light as only need some light so that the fish can experience a night/day cycle. Most likely will have a small layer of sand on the bottom of the tank, mainly for the mysis shrimp (a live food) which love to swarm over bright surfaces and when the fish get big enough and start to sift sand (thats if I get that far). Will also put a couple of small pieces of live rock in there, along with some smails to eat any algea and a cucumber to keep the sand stirred up. This will also be handy for the next time that I catch the shrimp releasing their larvae.

It is also getting very close to crunch time temperature wise. Yesterday it reached 40^oC here in Melbourne, phew that was hot, and it is only late November. I hope that this is not an indicator of how hot it will be in January. Anyway, I think that the ventilation fans coupled with the chiller will do a great job. These are not currently hooked up and working on OZ REEF, am waiting to complete the thermostats for them. The chiller works wonderfully though, as have already tested it out, so as soon as it is connected up, I am ready for some hot weather ;-) I actually constructed a thermostat using a circuit that I found online, but it did not work. Luckily I ran into an Electrical Engineer a couple of days ago, Andrew S., on #reefs (where would I be without it, most likely with more time to do other things, but hey) and he is now helping me with another circuit that will work and is more accurate. Thanks for your help Andrew, I really appreciate it.

This last month has also had its bad side in OZ REEF, a flame angel that moved into residency only survived 6 days :-( The reason for this is unclear, for more information see the Bereavement Notices.

As a little aside, I have some news from OZ RIVER (my freshwater aquarium). The various Crypts that I have in there have been sending out runners for over a year now, and the population have grown considerably. And this is an achievement in itself, but last week someone pointed out to me that they were flowering! Now this is ever so cool. It will be very interesting to watch the shot head towards the water surface and then flower when it reaches it.

Well, that is it for this month, and what a month it has been again. Oh, I am not sure how I will go with next month, it might not exist. It just depends on time, as I have a major project going in December. I am getting together my father's old Batallion mates to talk about their experiences in World War II. I hope to record the whole thing, make a transcript, and then put together a site with this transcript and further history of the Batallion.

Welcome OZ REEF's New Residents

• 1 x Centropyge loriculus, Flame Angel The final fish addition to OZ REEF, or that was the plan anyway. These are the most spectacular coloured angel, with this individual being red (as the species present around the Coral Sea are more red than those elsewhere) around the outer edges then transforming into orange in the center. The black vertical stripes are also well defined. But it was not to be :-(, see the Berevement Notices for more infomation.
• 3 x Cyprada annulus, Money Cowries As you may have realised by now, I love these snails. They do such a good job, and they are so unusual because of the mantle that they extend totally over the shell.
• 1 x Favites sp. Spectacular coloured coral, bright green high lights around the edge of the polyps, then bright red within this. The coral is also located on the end of an Acropora sp. skeletal branch, which makes it a dream to place on the reef structure.

Resident of the Month

Dear Marther ReefKeeper

How is it that a protein skimmer can remove substances from water?

From,
D.O. Carbon

Dear D.O.,

The following is how a protein skimmer works on the molecular scale:

Water is a wonderful solvent, being able to dissolve almost any substance. The reason for this 'universal' solvent property is the fact that it is a highly polar molecule. This means that there is both a positive and negative part within one molecule, but over all the molecule is neutral. Water, dihydrogen oxide, consists of two hydrogen atoms and one oxygen, H₂O. The two hydrogen atoms have a slight positive change, and the oxygen has a slight negative charge. So if a positive charged ion such as Ca²⁺, calcium, into water then water molecules will orientate themselves around the cation such that the oxygens are pointing in to stabilise the positive charge of the cation with the slight negative char ges. That is why ions are soluble in water.

Now the thing is, if you put something into water that has no charges, or differential charges on the molecule (non-polar), such as hydrocarbons, then the water molecule cannot stabilise it. Therefore it is insoluble in water, and this is the reason why petroleum products float or sink in water, and don't mix or are inmiscible.

If on the otherhand both of these two types of molecules, polar and non-polar, exist on the same molecule, then something very interesting occurs. A surface active molecule is generated. Within the molecule there are different parts; polar which can be stabilised in water (hydrophillic, water loving), and non-polar that cannot (hydrophobic, water hating). So how are both of these very different parts kept happy in water? Well, to do that the hydrophobic part has to get away from the water polar environment, and it can do this in several ways, depending on the environment. If there is only water present, and if the surface active molecule is of high enough concentration ,then it will form balls, called micelles. These consist of the surface active molecules orientated such that they hydrophillic part points out at the water, and that hydrophobic part points in. The hydrophobic parts are therefore in proximity with others of the same properties, and it generates its own non-polar envirionment within the highly polar environment of water. The hydrophillic parts point out, and can interact with water molecules, so both parts of the surface active molecule are happy.

If there exists an oil/water interface (non-polar/polar), such with petrol on top of some water, then the surface active molecule does not have to generate its own non-polar region to stabilise the hydorphobic in water. The surface active molecule will go to this interface oil/water interface, and orientate such that the hydrophillic part sticks into the water, and the hydrophobic part into the oil. This is exactly how surfactants work, such as detergents and how they remove dirt/oil.

Protein skimmers are very similar to this, but there is not an oil/water interface, but an air/water interface which is still non-polar/polar. The surface active molecules orientate at the interface in exactly the same way as with oil/water, with the hydrophobic section sticking into the air and the hydrophillic section remaining in the water. Protein skimmers generate a lot of small air bubbles, therefore this is a large area of air/water interface in a small volume. The surface active molecules stick to the bubbles surfaces, which increases the surface tension making the bubble much more stable. Therefore a foam forms within the riser tube of the skimmer, and the surface active molecules are removed from the water.

So as you can see a skimmer only removes a particular class of compounds from the water, that is molecules that have hydrophobic and hydrophillic sections. The remaining ones are left in the water. This is why it is recommended to use activated carbon as well, as this then removes more of the other organic molecules present in the water.

From,
Marther ReefKeeper

Tom's Bit

by Thomas S. Heo

Well, Tom is just way to busy now to put anything in on a regular basis. Therefore I am going to remove this section for OZ REEF Press, bummer that. But Tom has told me that he may write an article or two in the near future, may be on the small reef tank he now has on his desk at work. I look forward to it myself.

Special Feature

Bay Wash

by Bryony Bennett

Reprinted from CSIRO's science and environment magazine, ECOS.

At the entrance to Port Phillip Bay lies a menacing stretch of water known as The Rip. From Point Nepean, the western tip of Victoria's Mornington Peninsula, The Rip can be viewed in all its fury, writhing above a deep gorge in the sea floor.

Beyond The Rip stand the lighthouses of Point Lonsdale and Queenscliff, sentinels of the opposite shore. When seen on a map, this entry to the bay seems oddly undersized, as though a vengeful lunge of the sea thwarted nature's plan for a lake. For most ships only 300 m of the entrance is navigable: a hazardous welcome to Melbourne.

Satellite images of the bay reveal an added peril beyond this narrow gateway. Just inside the heads is the Great Sands region, a flood tide delta of extensive sand bars and shallows dissected by deeper channels. The 4000 or so ships entering the bay each year bound for Melbourne or Geelong are guided through The Rip and Great Sands by local pilots, experienced ship-masters wise to the bay's tides, contours and whims.

As well as governing the passage of ships, the bay's unique bathymetry greatly restricts water exchange with Bass Strait. Estimates of flushing times vary from near zero at The Rip, to 260 days in the middle of the bay and about 350 days in the Geelong arm of Corio Bay. This means that whatever flows in from the catchment has a long stay.

More than three million people live and work in the bay's catchment. The associated annual input of nitrogen from rivers, creeks, drains, sewage effluent and the atmosphere averages 7000 tonnes. Most of this total enters the bay as inorganic nitrogen, in the form of ammonia and nitrate. A major source of nitrogen is the Werribee sewage treatment plant, another is the Yarra River.

Between 1992 and 1996, an intensive study was conducted to determine the effects of these inputs, and to provide a scientific basis for managing the bay and its catchment. The Port Phillip Bay Environmental Study, designed and managed by CSIRO and funded by Melbourne Water, involved more than 47 individual research tasks. These were contracted to 29 state, national and international agencies and institutions.

The study found that despite these high inputs to the bay, nitrogen levels in the bay waters are much lower than in comparable bays and estuaries around the world. Phytoplankton levels - measured via chlorophyll a pigment - also are relatively low. Chlorophyll a commonly exists in Port Phillip Bay at one to two micrograms per litre, occasionally rising to 10. Similar water bodies elsewhere contain up to 50 micrograms or more.

This is good news for the bay's health. Most shallow water bodies with high nitrogen inputs and low flushing rates are at risk of eutrophication: excessive growth of a few dominant phytoplankton species. When this happens, the water becomes green and cloudy and seagrasses die from lack of light. Oxygen consumed during the plant's decay and the respiration of animals then exceeds the supply of oxygen from the atmosphere. Only bacteria that live on dead organic matter survive. These 'anaerobic' bacteria use carbon, sulfur and nitrogen compounds instead of oxygen to produce energy. The by-products are methane (marsh gas), hydrogen sulfide (rotten egg gas) and ammonia: all toxic to higher life forms.

Eutrophication is a state to be avoided. And so far it has been, thanks to the bay's oligotropic (low-nutrient) status. An explanation for the apparent vanishing of nitrogen in the bay waters had been sought in earlier studies. But it wasn't until the Port Phillip Bay Environmental Study that the phenomenon was understood.

A research task completed early in the study used purpose-built chambers to measure chemicals released from the bay sediments. The chambers were lowered onto the bay floor, effectively sealing off a quantity of water and sediment. Oxygen probes measured oxygen consumption over time, and water samples from the chambers were analysed for changes in their chemistry. Nitrogen was found to be released at levels much lower than expected, providing the first clue that processes occurring in the sediments must be taking up the nitrogen, thereby protecting the bay from eutrophication.

Another research task revealed the enormous magnitude and diversity of benthic (bottom-dwelling) fauna in the bay. It prompted a suggestion that benthic fauna might play a key role in nutrient turnover. Testing this theory required a deeper knowledge of the participants and processes in the bay's nutrient cycle.

Nutrients entering the bay are utilised by phytoplankton and other plants which are in turn consumed by zooplankton. Some nutrients are recycled, but most fall to the bay floor as faecal residues or dead algal cells. There they are taken up by invertebrates or single-celled algae (microphytobenthos), or decomposed by bacteria. Either way, the basic elements are converted back to their original inorganic forms of carbon dioxide, ammonia, nitrate, phosphate and silicate.

In many water bodies, these inorganic forms would diffuse upwards into the water and be recycled. If this recycling of ammonia and nitrate were to happen bay-wide, the ecosystem would rapidly become eutrophic. Water exchange with the ocean via Bass Strait would be too slow to prevent nitrogen accumulation. In Port Phillip Bay, however, nutrient recycling is limited by a series of processes occurring in the sediments which ultimately remove ammonia and nitrate from the water column as nitrogen gas.

Port Phillip Bay is mostly clear and shallow - the average depth is 13 m - so light penetrates through to the sea floor. Such conditions promote the proliferation of microphytobenthos, mostly diatoms, which glean inorganic nutrients from the sediments.

The sediments also house several hundred species of benthic invertebrates, or deposit feeders, which burrow some 50 centimetres in search of food. This expands the area of interface between the water column and the sediments, enabling oxygen to permeate the murky depths. As well as 'irrigating' the sediments with oxygen, the deposit feeders help to mix ammonia and nitrate into usually anaerobic sediments, and their faecal pellets encourage the presence of bacteria. These activities are known collectively as bioturbation.

Ammonia, upon reaching an oxygenated zone, is oxidised by bacteria to nitrate (nitrification). The nitrate diffuses into zones of low oxygen where other bacteria convert it to inactive nitrogen gas (denitrification). The nitrogen gas diffuses up into the water and eventually back to the atmosphere. Denitrification accounts for 80-90% of the nitrogen removed from the sediments and in so doing controls the degree of eutrophication in the bay. The bay's nitrogen cycle is almost entirely balanced by this process.

In a system devoid of bioturbation, anaerobic processes would dominate, because the aerobic zone would extend only a few millimetres into the sediment. Ammonia would not be nitrified, and its concentration would be much higher in the water column.

Research during the Port Phillip Bay Environmental Study found that burrows dug by one particular group of deposit feeders alone, the Callianassids, or ghost shrimps, increased the water-sediment interface by at least 8%. This adds up to an extra 8.6 km2 of interface below the sediment surface bay-wide. In effect, the deposit feeders build and maintain the bay's kidneys and lungs, keeping the system clean, and alive and breathing.

Clearly, protecting these hidden components of the bay ecosystem is vital to maintaining water quality. Given this need, an associated finding of the Port Phillip Bay Environmental Study offers cause for concern. Research by the Museum of Victoria found that benthic invertebrate numbers in the bay declined between 1969-73 and 1996. In addition, the proportion of filter feeders increased (from 23% to 33%) at the expense of deposit feeders (down from 71% to 55%).

The problem with this trend is that filter feeders rarely burrow. A shift towards filter-feeders at the expense of deposit feeders will result in a lower burrow surface area, and a consequent decrease in the mixing of oxygen, bacteria and ammonia through the sediments. Because these processes promote nitrification and denitrification, any further shift towards filter feeders may be detrimental to the bay.

These findings emphasise the need to monitor benthic populations on an ongoing basis. Bioturbation effects and rates can be investigated via experiments, but if population densities are not available for a system, bay-wide extrapolations cannot be made. With no warning system in place, the chances of repairing the bay's vital organs would be slim.

Defining the danger zone

Results of the diverse field surveys and experiments conducted during the Port Phillip Bay study have been integrated in a mathematical model that simulates physical and ecological processes occurring in the water column and sediments. The Port Phillip Bay model, developed by scientists from CSIRO's Division of Marine Research, can predict the critical nutrient loading at which eutrophication of the bay is likely to occur.

The most sensitive indicator of the trophic state of the bay is the nature of nitrogen release from the sediments. In the main bay, denitrification is the dominant process. As explained earlier, this is the desirable state. In some places, however, such as Hobsons Bay at the mouth of the Yarra River, nitrogen is released in the form of ammonia. This is not desirable and is an indication that the sediment system has been overloaded.

Denitrification efficiencies are maximised at intermediate nitrogen loads. The biomass of benthic invertebrates increases as water column production increases, but only up to a point. Benthic communities become depauperate, burrowing species disappear and bioturbation ceases if the sediment surface is too heavily loaded with decomposing organic material so that anoxia results. Under these circumstances, nitrogen is buried rather than denitrified and there is a significant release of ammonia to the water column. Also, there are major changes to the bacterial flora of the sediments.

The model estimates the critical catchment load at which sedimentary anoxia would begin as somewhere between double and treble the present loadings: about 17 000 tonnes of nitrogen a year. This is the irreversible point at which permanent eutrophication of the bay would occur.

Clearly it is desirable to maintain denitrification efficiency in the bay. This will ensure the long-term health and stability of the bay and provide some cushion against unforeseen extreme events. To achieve this, the Port Phillip Bay study team recommended a precautionary reduction in total nitrogen loads of about 1000 tonnes per year, particularly in the loads from the Yarra River and major creeks and drains in the urban area.

The potential benefits of such a strategy were illustrated during the 1994 drought when inflows from the Yarra River, creeks and drains were greatly reduced. During this time the bay became more oligotrophic and chlorophyll concentrations dropped to the lowest levels for years. The abundance of algae around the margins of the bay also dropped. Reduced storm inflows and urban run-off clearly can have a marked effect on the primary production and water quality of the bay.

The Port Phillip Bay study team concluded that a reduction in the total nitrogen load to some 6500 tonnes a year would rapidly show sustained improvements in water quality. At the very least, present levels should not be exceeded. They should certainly never be allowed to reach double present loadings.

Finally, the study team recommended that the bay be seen as an integral part of the entire regional development plan tor the Melbourne. In the longer term, the key to the bay's successful management would be to develop models linking the hay to the city and its catchments. This would enable the impact of water supply, sewage and catchment management options to be objectively assessed, thus ensuring that dubious welcome to Melbourne entails no more than a rough ride through the gate.

Melbourne Water has a summary of the Port Phillip Bay Environmental Study on the Internet at http://www.melbwater.vic.gov.au

You Wouldn't Believe It!

..... flatworms, members of the Phylum Platyhelminthes do not have any circulatory system, respiratory gills, or an anus. Respiration occurs by the means of diffusion, with oxygen diffusing into the body, and carbon dioxide out. This is one of the main reason that they are so flat, otherwise the oxygen and carbon dioxide would have to diffuse too far, and the worm would not be able to supply enough oxygen, or remove the carbon dioxide fast enough. Flatworms are typically mistaken for nudibranchs, but the fast that they have no external respiratory gills allows indentification. Food is also distributed throughout the body by diffusion.

..... in a recent scientific study, fish fry released during the day from outside the boundaries of a reef always swim away into open water. This is thought to be a survival behaviour, as there are heaps of hungry fish present on the reef that would love to make a meal of the fry. The actual way in which the fry determines in which direction the reef is, is still undertermined. But it is hypothosised that it is the noise of a reef, various noises made by fish present there, current surges, wave breaking, and may be even the sound of parrot fish as they go about chewing on the reef.

Bereavement Notices

Centropyge loriculus
This is a very depressing death :-( He was only in OZ REEF for 6 days, then one morning find him dead. Settled in very well to the tank, showed no signs of stress and cruised around the tank. Was also feeding, taking brine shrimp, trying a bit of the seafood mix I makes, and eating the nori that it contained. Had a full stomach, and no external signs of anything wrong. Then gone. This is a big, big mystery. Checked the body for any unusual signs/features, but looked like a perfect individual. Rather expensive fish too, $100. I am still undecided if I will try another flame angel, but have also been thinking about may be a sailfin tang. I think I will just sit on this for awhile, there is no hurry.

Fromia indica
Seems like the three time death of starfish that I had about 2 months ago has repeated itself, in the way the starfish died that is. I have indetified the cause of what it was 2 months ago, the addition of around 15kg of live sand. This has appeared to have cause some type of osmotic shock to the water vascular system of the starfish, and then they just fell apart. The death of the Fromia indica in this past week occured in the same way. The starfishes arms start to no longer attach to the rock, and only move along on the inner parts of the arms. Then one of the arms start to disintergrate, just fall apart. This spreads down the arm, and then begins on other arms, and continues until the entire starfish is consumed or vital organs near the oral disc are effected. The cause of this latest death is unknown, there were no environment shocks to the water that can be identified. Only option left is that the starfish starved, but this seems unlikely as from all sources these starfish have been identified as detrivours.

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