At Macca this week — what are we doing about marine debris? And, just how much ozone is above us?

A blitz on marine debris

The significance of World Environment Day (5 June) was certainly not overlooked by the Macquarie Island team. The team pulled together throughout the month of June to undertake a series of coordinated marine debris collection trips to the remote west coast of Macquarie Island. The target area — a 8 kms long section from Sellick Bay to Cape Toucher. 

For most of the year, this section of coast line has restricted access to allow for the undisturbed breeding of sensitive Giant Petrels. A brief gap in the breeding cycle occurs during June and July, allowing teams to set about the task of the debris recovery along the rocky coast. The old saying of the ‘journey not so much the destination’ certainly comes to mind here.

Each team typically covers about 55kms over the duration of their four days in the field. In real terms, the teams only get to cover 1–1.5kms of the target area, over about a 2hr period — the rest of the time is spent getting to and from the location! The short daylight hours for this time of year severely limit the amount of time that can actually be spent picking up rubbish. Not everyone can be in the field at the same time — the half way accommodation at Davis Point can only hold three people at a squeeze! Mind you the willingness of fellow expeditioners to swap station duty rosters and keep the home fires burning certainly makes it easy for the rest to head off to the field! The motivation of removing rubbish from what should be a pristine piece of shore is certainly high on everyone’s agenda, although the chance to spend some time exploring a typically inaccessible remote section of the island, as well as camping overnight in a water-tank hut is not overlooked. 

Under the coordination and guidance of Ranger-in-Charge Chris, teams of three at a time have set about the task of scouring the boulder strewn coastline. Each team has been allocated a discreet section of coast working from Sellick Bay in the north towards the half way point of Davis Point, then if time permits on to Cape Toucher. Rubbish recovered has been added to existing marine debris caches already established at strategic locations — each sited for potential recovery via support of helicopters during island resupply later in the season. 

Efforts from previous years have revealed large quantities of rubbish of all sorts from floats and buoys to plastic bottles, rope string nets and large quantities of micro plastics. 

The task is only partly completed but results thus far have been very promising with an amazing decrease in the amount of rubbish recovered. The usual array of plastic bottles, the odd fishing float, small quantities of rope, one gum boot and one old hard hat are typical of what has been collected so far. 

The ozone above Macca

Here at Macca we release two weather balloons a day, everyday. On Wednesdays, (if the weather cooperates) we release an extra big balloon, the 1200g, to carry the ozone sonde aloft to around 35km above the surface. We use the ozone sondes to measure the ozone gas concentration in the atmosphere above Macquarie Island.

Most of the ozone in the atmosphere is between 15 and 30km above the earth’s surface in the stratosphere. As you may know, this ozone layer is very important for protecting those of us living on earth from harmful UV (Ultraviolet radiation) radiation. After the discovery of the ozone hole in the 1970’s the Montreal Protocol on substances that deplete the ozone layer was agreed in 1987. A part of this international agreement includes monitoring the ozone layer. The Bureau of Meteorology has ozone-monitoring locations spread across different latitudes including Melbourne, Brisbane, Darwin, Perth, Davis (Antarctica), and Macquarie Island. The different sites take a mix of ozone sonde and Dobson spectrophotometer observations. The Dobson spectrophotometer is an instrument that measures ozone by comparing the amount of sunlight at two UV wavelengths. One wavelength is affected strongly by ozone, the other is not. The difference between the two is directly related to the total column ozone. 

An ozone sonde contains an electrochemical cell and a small pump that draws air though the cell. The solution in the cell reacts with the ozone, producing a small electric current that is directly proportional to the ozone amount. The setup and calibration of the ozone sonde is a time consuming process, with two stages completed over the 10 days before the balloon release. We are therefore a little bit fussy about the weather on day we are due to release the ozone sonde. Too windy and the sonde may go crashing into the ocean, destroying all our work, too wet and we cannot take Dobson readings.

On the flight day, we connect the ozone sonde and attach a radio sonde to the side. The radio sonde monitors temperature, humidity and pressure and uses its GPS to calculate wind speed and direction while the ozone sonde gives a vertical profile of ozone through the atmosphere. After a successful balloon release, we monitor the data from the sondes on our computer system before emailing it for processing in the Bureau of Meteorology’s Melbourne office. We also take several Dobson readings every day at Macquarie Island. The Dobson measurements give a total ozone reading that is less detailed than the information from the ozone sondes. Dobson readings are used to collaborate the data from the ozone sondes and polar orbiting satellites that monitor ozone.

By Vicki, Senior Observer Macquarie Island