Professor Jennifer Verduin

The greater Southeast Asian region contains the largest global extent of tropical seagrass; however, anthropogenic degradation is estimated to be greater than 7% per year. Although the areal extent of seagrass is presently 36,765 km 2 , Fortes group estimates that 50% of the original seagrass has been degraded from a variety of impacts. One set of solutions to degradation is to restore tropical seagrass successfully, for which information from past results is needed to avoid failures. Van Katwijk, Thorhaug and others provided a global seagrass restoration review of 1,786 trials, but did not include the full Southeast Asian regional information. Thus, we review findings from 228 trials in the greater Southeast Asian region, involving 305,807 restored units with an extent of 372,649 m 2 . Seagrasses planted with varying successes include 13 tropical species and five subtropical or near-subtemperate species. We compare methodologies as well as key factors of light level, energetics, and depth. This review demonstrates the highest survival in seagrass restoration employing sprigs or plugs at medium depths (2–4 m) with adequate light levels in medium to low energetics planting one to several dominant species. Substrate anchors improved successful establishment. Information gaps occur in quantified monitoring of seagrass services reassembled with tropical-seagrass restoration; thus, fisheries’ nursery potentials are not provided. Future actions need national seagrass restoration policies and plans to restore degraded seagrasses. At present, such policies and plans are non-existent in most greater Southeast Asian regional nations, with the exceptions of Australia and the Philippines, although some nations have national plans for restoring corals or mangroves.

Seagrass loss is impacting coastal communities globally, and significant efforts are being spent to address this loss through restoration. Yet, the success of restoration projects and methodologies has rarely been assessed over decades. In this case study, we reviewed past and continuing seagrass restoration projects (66 restoration sites from 1990s to 2020s) in Cockburn Sound and Owen Anchorage, temperate Western Australia, to (1) address whether they were successful in rehabilitating seagrasses, (2) whether seagrasses could be restored at appropriate scales, and (3) what the requirements for successful seagrass restoration were. In 2022, 28 individual restoration sites were revisited to establish long-term restoration success. Methods of seagrass restoration included shoots (as sprigs, plugs, cores, and sods), seedlings, and seeds. Approximately 70% of sites revisited in 2022 showed demonstrable success in restoring seagrasses. Project extent ranged from meters to hectare scales, including a study that restored 3 ha using sprigs. In the 2010s, seed-based restoration research became a major success at hectare scales. Pre-existing environmental conditions and processes were extremely important in determining restoration success, which was both site-and time-specific and influenced the choice of restoration methods. Restoration required the environment to be suitable for natural seagrass revegetation, or it needed modification. Researchers' focus on small-scale experiments testing methods across a range of environments has prepared us for scaling up to hectares. In long-lived seagrasses, decades of hysteresis were overcome with restoration, as it assisted natural recovery.

Globally, the presence of microplastic materials in the environment is widespread, and their largest concentrations can be found in coastal ecosystems and within mid-ocean gyres. Since the inception of mass plastic product manufacturing in the middle of the twentieth century, these durable, lightweight, and inexpensive materials have been, and continue to be, extensively exploited by humans. However, the presence of large numbers of microplastics in marine ecosystems in recent years has become a serious environmental issue that has attracted widespread interest in both the scientific and the broader community at large. In particular, the ingestion and subsequent detrimental health effects on many marine species are the most noticeable and alarming impacts of microplastics. Furthermore, recent studies have also shown microplastics can accumulate, concentrate, and act as vectors for conveying toxic pollutants within the food chain. Another feature of microplastics is their ability to transport marine species from one ecosystem to another where they become threats to local indigenous marine species. Because of the serious nature of microplastic pollution, it is important to understand their impact on coastal ecosystems and ocean gyres. This chapter discusses four aspects of microplastic pollution: 1) sources of both primary and secondary microplastics; 2) their physical and chemical behavioral properties; 3) bioavailability and behavioral properties of microplastics and their interactions with marine organisms; and 4) future perspectives, which highlights key areas of research needed to elucidate the effects of microplastic pollution in the marine environment. Importantly, understanding these four aspects of microplastic pollution will assist in directing future marine pollution research and assist policymakers to develop appropriate management strategies.

To determine volume and heat transports through Fram Strait, an array of current meter moorings was maintained in the Strait between 1997 and 2001, with annual redeployments. The transports obtained by averaging the monthly means from the first 2 years were 9.5 Sv to the north and 11.1 Sv to the south (ISv = 106m3s-1). The net transport over the 2 years was 4.2 Sv to the south, taking into account that there is some recirculation from the eastern to the western side of the transect which has a meridional offset of 10 nmi. The northward transport consists of about 50% of Atlantic Water, of which about 65% recirculates north of the transect. The northward heat flow, 85% of which is by Atlantic Water, is 16TW (1997/1998) and 41TW (1998/1999).

The ever-increasing use of plastic materials has also led to high levels of waste entering the environment and becoming a serious pollutant. To determine and expand knowledge of microplastic pollution in the marine environment, the present case study examines South Beach sediments. South Beach is adjacent to Cockburn Sound (Western Australia) and is made up of four smaller beaches. Each of these small beaches are each separated by a groyne. The study considered the abundance and spatial distribution of microplastic fibers in the beach sediments. The analysis technique used density separation, via a new elutriation system using hyper-saline solutions, to separate microplastic fibers from sandy beach sediments. Recuperation rates of around 95% were achieved for plastic densities ranging from 0.9 to 1.3 kg m-3. Recuperation rates for plastic densities greater than 1.4 were around 84%. The overall mean microplastic fiber density for South Beach was found to be 43.3 fibers kg-1. The fibers ranged in size from 800 to 1,824 microns, and the mean size was estimated to be 1168 ± 274 microns. The novel elutriation system developed for this study was found to be ideal for routine monitoring programs.

Globally, the presence of microplastic materials in the environment is widespread, and their largest concentrations can be found in coastal ecosystems and within mid-ocean gyres. Since the inception of mass plastic product manufacturing in the middle of the twentieth century, these durable, lightweight, and inexpensive materials have been, and continue to be, extensively exploited by humans. However, the presence of large numbers of microplastics in marine ecosystems in recent years has become a serious environmental issue that has attracted widespread interest in both the scientific and the broader community at large. In particular, the ingestion and subsequent detrimental health effects on many marine species are the most noticeable and alarming impacts of microplastics. Furthermore, recent studies have also shown microplastics can accumulate, concentrate, and act as vectors for conveying toxic pollutants within the food chain. Another feature of microplastics is their ability to transport marine species from one ecosystem to another where they become threats to local indigenous marine species. Because of the serious nature of microplastic pollution, it is important to understand their impact on coastal ecosystems and ocean gyres. This chapter discusses four aspects of microplastic pollution: 1) sources of both primary and secondary microplastics; 2) their physical and chemical behavioral properties; 3) bioavailability and behavioral properties of microplastics and their interactions with marine organisms; and 4) future perspectives, which highlights key areas of research needed to elucidate the effects of microplastic pollution in the marine environment. Importantly, understanding these four aspects of microplastic pollution will assist in directing future marine pollution research and assist policymakers to develop appropriate management strategies.

Sea level exerts a fundamental influence on the intertidal zone, where organisms are subject to immersion and emersion at varying timescales and frequencies. While emersed, intertidal organisms are exposed to atmospheric stressors which show marked diurnal and seasonal variability, therefore the daily and seasonal timing of low water is a key determinant of survival and growth in this zone. Using the example of shallow coral reefs, the coincidence of emersion with selected stressors was investigated for eight locations around the Australian coastline. Hourly water levels (1992 – 2016) from a high-resolution sea level hindcast (http://sealevelx.ems.uwa.edu.au), were linked to maximum surface solar radiation data from the Copernicus ERA5 atmospheric model and minimum atmospheric temperature observations from the Australian Bureau of Meteorology to identify seasonal patterns and historical occurrence of coral emersion mortality risk. Local tidal characteristics were found to dictate the time of day when low water, and therefore emersion mortality risk occurs, varying on a seasonal and regional basis. In general, risk was found to be greatest during the Austral spring when mean sea levels are lowest and a phase change in solar tidal constituents occurs. For all Great Barrier Reef sites, low tide occurs close to midday during winter and midnight in the summer, which may be fundamental factor supporting the historical bio-geographical development of the reef. Interannual variability in emersion mortality risk was mostly driven by non-tidal factors, particularly along the West Coast where El Niño events are associated with lower mean sea levels. This paper highlights the importance of considering emersion history when assessing intertidal environments, including shallow coral reef platform habitats, where critical low water events intrinsically influence coral health and cover. The study addresses a fundamental knowledge gap in both the field of water level science and intertidal biology in relation to the daily timing of low tide, which varies predictably on a seasonal and regional basis.

Outdoor studies were conducted on microalgae cultures in two raceway ponds (kept in constant motion with either jet or paddlewheel) with a flatbed to treat anaerobic digestion piggery effluent and to observe the characteristics of turbulence on microalgal mixing and growth. Acoustic Doppler Velocimeters (ADV) were deployed to record the instantaneous velocity components and acoustic backscatter as a substitution of microalgae concentration. The present research on microalgal mixing considers the effect of event-based turbulent features such as the widely known ‘turbulent bursting’ phenomenon. This is an important aspect, as turbulent coherent structures can result in microalgal mixing, which can lead to significant changes in microalgal growth. The experimental results presented in this paper of two contrasting environments of jet- and paddlewheel-driven ponds suggested that: (1) turbulent bursting events significantly contributed to microalgal mixing when paddlewheels and jets were used; (2) among four type of turbulent bursting events, ejections and sweeps contributed more to the total microalgal mixing; and, (3) a correlation was revealed using wavelet transform between the momentum and microalgal mixing flux when either jet or paddlewheel were used. Such similarities in jet and paddlewheel raceway ponds highlight the need to introduce turbulent coherent structures as an essential parameter for microalgal mixing studies.

The estimation of the time since death (minimum Post Mortem Interval, minPMI) is an essential aspect of forensic investigations. This is particularly complex when a human body is found submerged, floating or beached in a marine environment. When a cadaver is found in a terrestrial environment the minPMI estimation is generally based on the presence of carrion insects. However, when a cadaver is found in an aquatic environment, a correct crime scene reconstruction is more complex and requires the consideration of the time the remains spent submerged underwater (minimum Post Mortem Submersion Interval, minPMSI) and/or floating (Floating Interval, FI). In marine crime scene scenarios, the use of barnacles (Crustacea: Cirripedia) has recently received some attention, due to their permanent settlement on human remains and their accompanying clothing. Previous research considered barnacle growth on human shoes, but the present research is the first to focus on the colonisation of barnacles on clothing materials (fabrics). Polystyrene floats were covered by either cotton, velvet, satin or neoprene and submerged underwater over a period of six months off the coast of Perth, Western Australia. The aims of this research were 1) the identification of marine species colonising the fabrics, with special attention to barnacles; 2) the identification of which fabric type provides the most desirable environment for colonisation; and 3) the identification of factors that affect the growth rate of the different species. Three species of barnacles, Balanus trigonus Darwin, Amphibalanus reticulatus (Utinomi) and A. variegatus (Darwin), were present in varying numbers and sizes. The colonisation process of the barnacles occurred rapidly, with the first sighting of barnacles observed within the first month on neoprene and control floats. The surface that attracted the largest number of barnacles was neoprene, followed by satin and cotton, while velvet showed an inconsistent colonisation rate. The largest size barnacles were observed on the control floats, while all fabrics showed a similar smaller size. Overall, time spent in water and water temperature had a significant positive relationship with both number and size of the colonising barnacles. This study is the first to provide information that will aid in the investigation of human remains recovered from Western Australian marine waters, using the barnacle colonisation on different fabric types.

Seagrass habitats at the Cocos (Keeling) Islands (CKI), a remote atoll in the Indian Ocean, have suffered a catastrophic decline over the last decade. Seagrass monitoring (1996–2020) in relation to dredging and coastal development works (2009 to 2011) provide a historical baseline, and document the decline of mixed tropical seagrass Thalassia hemprichii and macroalgal (predominantly Caulerpa spp.) beds over a decadal scale time series. Attribution of loss to coastal development is confounded by lagoon-wide die-off events in 2007, 2009 and 2012 and high air and water temperatures from 2009 to 2016, with evidence of broad scale changes, visible in satellite imagery between 2006 and 2018. We conclude that up to 80% of seagrass habitats in the CKI lagoon (~1200 ha) have been lost due to multiple stressors including episodic die-off events related to high temperatures and calm conditions, and loss due to sediment disturbance and increased turbidity. Grazing pressure from the resident green sea turtles (Chelonia mydas) may have also exacerbated the loss of seagrass, which in turn poses a dire threat to their ongoing health and survival. This study highlights the fragility of tropical seagrass habitats and the cascading effect of system imbalance as a result of anthropogenic pressures and climate drivers. Although small in comparison to global estimates, the loss of seagrass habitats at CKI could change the entire ecosystem of a remote atoll. Due to the significance of the Thalassia beds for coastal stability, as food for an isolated population of green sea turtles and as a fish nursery, rehabilitation efforts are warranted.