Dr Bruce Hodgson

A sustainable global net-zero carbon emission is when emissions are equivalent to the uptake of carbon by global terrestrial and aquatic plants. To meet that objective, an approximate 50% reduction of fossil-fuel emissions was estimated for net-zero by 2050 using carbon dioxide concentrations and mass emission monitoring by NOAA and related references. From that data, the initial target level of reduction to obtain net-zero was selected for year 2000 to minimise effects of climate change on environmental damage. The recent finding that about half global emissions are taken up from the atmosphere and increases global terrestrial and aquatic plant growth, including agriculture plants for food production, indicates it is important to maintain the year 2000 levels in the atmosphere. It was concluded as renewable energy was found to need support, it could be supplemented by electricity production remaining after obtaining net-zero, which also supports the atmospheric carbon dioxide levels for their important global ecological contribution.

The aim of this study was to apply Zostera capricorni growth rate mathematical solutions to saline coastal lagoons to generate novel mathematical insights that could be used by estuary managers in other estuaries and saline lagoons. It is proposed that the quadratic curvilinear 2 nd Order relationships of seagrass growth rates with water temperature and subsurface light intensity, and with linear relationships for sediment total phosphorus, have the potential to inform catchment runoff management strategies by applying the equations to similar data obtained for other Zostera species in coastal lagoons and estuaries. The equation for water temperature includes an expected 1.4°C increase due to climate change in the seagrass beds, which was consistent with the derived water temperature equation. Thus, the detailed data and information obtained from the online and published studies of Zostera provided important biological processes for assessing the likely effects of the three main environmental drivers on seagrass growth rates. Analysis of the data determined the optimum temperature, light intensity thresholds before photo-inhibition, and a benchmark for sediment total phosphorus (TP) associated with growth rates and higher and more stable biomass in the urbanized areas of the studied lagoon system. The relationship between Zostera biomass and TP indicates the possible optimization of seagrass biomass by catchment nutrient runoff.

The main diet of baleen whales is krill in the Arctic, Antarctic and during migrations in the Atlantic, Pacific and Indian Oceans. Hence, the aim of this paper is to quantify the global importance of the krill to baleen whale component of the pelagic food web and possible feedback loops. That was undertaken by comparing the results of Ecopath Models in the Antarctic and Arctic Oceans and to migration areas in the North Atlantic and Alaska, was well as the large Seamount area from the Antarctic and Arctic. Biological production transfer is the essential component of the prey to predator pelagic food web, which maintains the production of predators. The importance of sustaining global baleen whale migrations is to support ecosystem production by whale defecation contribution to nutrient recycling. It is important to sustain krill and fish abundance in whale migration feeding areas using ecosystem-based fishery management (EBFM) fishing rates. It was shown by the literature that migrations tended to followed deep-sea seamounts, and baleen whale defecation and nutrient cycling at seamounts led to the effects of nutrient upwelling by deep sea currents at seamounts. Hence, it is suggested seamounts be protected as important marine ecosystems. Therefore, those processes indicate sustaining krill and whale abundance is likely to support global marine ecosystem stability in open ocean migration areas.

Antarctic krill is an important component of the zooplankton production in the Southern Ocean and is a major food source for baleen whales. The role of commercial fishing and predation by whales on Krill abundance has been investigated here using the innovative ecosystem-based fishery management, EBFM which maintains the krill to whale food web ecosystem stability. The literature indicates the Krill fishery may have been overfished, so it was reduced to the current annual upper limit of 0.62 million tonnes for support other predators of krill, such as seals, penguins and flying sea birds. However, recent literature suggests a moderate reduction in krill catch in the Antarctic Peninsula area due to its importance for whale migration to temperate areas. The Peninsula area catch was estimated to be reduced by about 10% due to additional concerns about climate change effects on krill abundance in the Southern Ocean, reducing overall catch to 0.556 million tonnes, moderately higher than the maximum taken in 2022. Hence, the krill biomass fishing was reduced to allow for predation by baleen whales and other predators, giving a full ecosystem-based fishing mortality similar to that previously estimated to maintain krill production in the Southern Ocean.

The aim of this paper is to develop a methodology to estimate recovery times using a wide range of published Ecopath modeled overfished data-rich fisheries that had not recovered in the North Sea, Mediterranean, and South America shelves. Recovery times were estimated by biomass increase according to the Verhulst logistic equation mathematical solution, requiring the intrinsic rate of natural increase, r, and the carrying capacity for a fishery, K E , both derived from documented fishery biological process principles. The mathematical solution indicated recovery from <0.2K E may be possible, initially to the minimum overfished level, B OF , of 0.25, then recovered, B REC , 0.4 of the fishery carrying capacity. It was estimated recovery in about 5 to ≤10 years could be obtained with fishing mortalities at half the intrinsic rate of natural increase. Recovery may require fishery stakeholders to select various strategies for recovery, including potential limitations by phytoplankton production in the fishery area. The documented recoveries for fishery areas of the sardine Namibian shelf fishery and climate-related temperature changes and upwelling effects on biomass of the hake fishery in the northern North Sea and West of Scotland shelves are used as examples. The potential recovery of a data-limited fishery is also shown using the relationships derived from the biological processes of data-rich fisheries. Further research is suggested on how to estimate the biomass of data-limited fisheries for recovery from overfishing.

Following the planned FAO Ecosystem Restoration Programme for estuarine habitats to support estuarine fisheries and early life stages of estuary-dependent marine fish, direct relationships of total seagrass and eelgrass Zostera m. capricorni areas and biomass with fish harvest were derived for a range of slightly to highly urbanized coastal lagoons that are expected to support the larvae and juveniles of estuary-dependent marine fisheries. Fish harvest and seagrass area and biomass in the lagoons increased with moderate catchment total suspended sediment and total phosphorus loads due to lagoon flushing rates directing excess silt and nutrients out to sea via the lagoon entrances. Well managed, sewered catchment management works are shown that could assist estuary managers maintain seagrass for estuarine and offshore estuary-dependent fisheries by maintenance of seagrass and fishery ecological processes. Further research is suggested to investigate estuary-dependent post-juveniles leaving estuaries and lagoons migrating to nearshore, offshore and shelf marine fisheries.
•Coastal lagoon seagrass for larvae and juveniles of estuary-dependent marine fish.•Relationships of Zostera m. capricorni areas and biomass with fish harvest.•Increased seagrass and fish harvest with moderate sediment and phosphorus loads.•Increases aided by flushing rates transport nutrients to sea via lagoon entrances.

A theoretical basis for Ecosystem-based Fisheries Management (EBFM) was derived for pelagic fish by applying marine ecology theory of analytical relationships of predator-prey biological production transfers between trophic levels to FAO guidelines for an ecosystem approach to fisheries. The aim is to describe a simple method for data-limited fisheries to estimate ecosystem-based F MSY and how EBFM modellers could mimic the way natural fish communities function for maintaining ecological processes of biological production, biomass and ecosystem stability. Ecosystem stability (ES) F MSY were estimated by proportion of biological production allocated to predators, giving ES F MSY of 0.23 for small pelagic and 0.27 for pelagic finfish, prioritising ecosystem over economics. To maintain both stability and bio-mass (SB) a full pelagic EBFM SB F MSY of about 0.08 was obtained for both small pelagic and pelagic finfish, having mostly ecosystem considerations. As the F MSY are single-species averages of catchable species targeted in a specific trophic level, multispecies fishing mor-talities were proportioned by the biological production of each species in the trophic level. This way catches for each species are consistent with the average ecosystem F MSY for a trophic level. The theoretical estimates gave similar results to other fisheries for sustainable fish catches that maintain the fishery ecosystem processes. They were also tested using six tropical Ecopath Models and showed the effects of imposing commercial fishing mortalities on predominantly EBFM conditions. The ecosystem stability ES F MSY is suggested to be investigated for sustainable fish catches and the full EBFM SB F MSY for protected areas or recovery of heavily depleted stocks.

Nutrient fluxes and primary production were examined in Lake Illawarra (New South Wales, Australia), a shallow (Zmean=1.9 m) coastal lagoon with a surface area of 35 km2, by intensive measurement of dissolved nutrients and oxygen profiles over a 22-h period. Rates of primary production and nutrient uptake were calculated for the microphytobenthos, seagrass beds, macroalgae, and pelagic phytoplankton. Although gross nutrient release rates to the water column and sediment pore waters were potentially high, primary production by microphytobenthos rapidly sequesters the re-mineralized nutrients so that net releases, averaged over times longer than a day, were low. Production in the water column was closely coupled with the relatively low sediment net nutrient release rates and detrital decomposition in the water column. Dissolved inorganic nitrogen and silica concentrations in the water column are drawn down at the beginning of the day. The system did not appear to be light limited so photosynthesis occurs as fast as the nutrients become available to the phytoplankton and microphytobenthos. We conjecture that microphytobenthos are the dominant primary producers and, as has been shown previously, that the nutrient uptake occurs in phase with the various stages of the diatom growth.

Investigation of role of zooplankton feeding by coral at Heron Island in the southern Great Barrier Reef. It was estimated that coral obtained 10% of its carbon by consumption of zooplankton and 90% by photosynthesis. The zooplankton consumption was an important part of the coral symbiosis as it provided nitrogen and phosphorus to support zooxanthellae photosynthesis in a low nutrient aquatic environment.