MAC SAFE HARBOUR
THE health of Macquarie Harbour is improving three years after low oxygen and high bacteria levels prompted the environmental watchdog to tell fish farmers to reduce their impact on the environment.
The latest environmental health report card shows oxygen levels have increased, sediment conditions are better and bacteria mats have reduced.
The report also says the abundance of fish and the number of species had also returned to those seen before 2016 — when the same report card forced Tassal, Petuna and Huon Aquaculture to make major changes to their practices there.
Institute for Marine and Antarctic Studies research fellow Dr Jeff Ross said conditions were improving but there was still a way to go. Oxygen levels, for instance, were still lower than historical observations.
THE health of Macquarie Harbour is improving three years after low oxygen and high bacteria levels prompted Tasmania’s environmental watchdog to tell fish farmers to reduce their impact on the environment.
The latest environmental health card shows oxygen levels have increased, sediment conditions are better and bacteria mats have reduced.
The report also says the abundance of fish and the number of species had returned to almost that seen before the harbour’s health declined in 2016.
The Institute for Marine and Antarctic Studies yesterday released the latest results of its surveys of the West Coast harbour, carried out as part of ongoing monitoring of oxygen dynamics and conditions on the bottom.
IMAS Research Fellow Dr Jeff Ross has tempered the better results saying while the trend was encouraging, oxygen levels were still lower than historical observations.
The report card issued in 2016 was dire and prompted a warning from Tasmania’s environmental watchdog to Tassal, Petuna and Huon Aquaculture to lift their game.
Dr Ross said that in 2018, oxygen levels in the middle and bottom waters of Macquarie Harbour declined in spring but not for as long, or to the same extent, as was seen in recent years.
“This improvement was reflected in the latest survey of seabed conditions that we carried out early this year,” he said.
“The abundance and numbers of benthic species at most sites were in better shape than observed in recent years over the summer months.
“We continue to see improved conditions in our video assessments of the seabed, and the presence of beggiatoa bacteria mats was also lower this summer compared with previous years.”
Beggiatoa was observed on 13 of 51 lease dives — less than in the last three surveys in January, May and September last year.
At the external sites, beggiatoa was observed at four of the 28 sites and in all cases noted as patchy or thick patchy.
Dr Ross said that while the trend of improving harbour health over recent years is encouraging, oxygen levels are still lower than observed historically.
“Our team has just returned from a survey of sediment conditions in June, and another is scheduled for January 2020, and we will also continue to monitor oxygen levels in real time throughout the harbour,” he said.
“These observations will provide us with a growing body of data about how well the harbour is recovering following the major deterioration in conditions reported in spring 2016.”