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Introduction
Peter Todd is an Associate Professor at the Department of Biological Sciences, National University of Singapore, where he runs the Experimental Marine Ecology Laboratory.
Publications
Publications (246)
As coastal cities around the world expand, and sea levels and the frequency of storms rise, natural shorelines are steadily being replaced by artificial defences such as seawalls. A growing number of studies have documented the assemblages that inhabit these novel environments, and some have contrasted them against those found in their natural anal...
Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Dat...
Over the last decade there has been a global effort to eco-engineer urban artificial shorelines with the aim of increasing their biodiversity and extending their conservation value. One of the most common and viable eco-engineering approaches on seawalls is to use enhancement features that increase habitat structural complexity, including concrete...
Human population density within 100 km of the sea is approximately three times higher than the global average. People in this zone are concentrated in coastal cities that are hubs for transport and trade – which transform the marine environment. Here, we review the impacts of three interacting drivers of marine urbanization (resource exploitation,...
Coral reefs worldwide are facing multiple severe stressors leading to ecosystem degradation, but local extinctions of species are not well documented. Here, we track the diversity of Pocilloporidae Gray, 1840 coral species—many of which are known to be sensitive to environmental disturbances—on Singapore reefs through time, integrating information...
Increasing coastal development and global warming have resulted in large-scale habitat changes, with artificial coastal structures replacing extensive tracts of natural shores. In Singapore, for example, more than 63% of the natural coastline has been replaced by seawalls. Multiple studies from both temperate and tropical regions have compared spec...
Despite seawalls becoming ubiquitous coastal features, and having some physical similarities to natural rocky shores, it remains unclear how these urban habitats influence predator–prey interactions. Predators can affect intertidal mobile prey densities through two pathways: (1) successful predation directly influences prey mortality rates, and (2)...
Characterisation of genomic variation among corals can help uncover variants underlying trait differences and contribute towards genotype prioritisation in coastal restoration projects. For example, there is growing interest in identifying resilient genotypes for transplantation, and to better understand the genetic processes that allow some indivi...
The diversity‐habitat complexity relationship has been utilised widely in conservation and biodiversity enhancement interventions, but few studies have attempted to tease apart the components of complexity that drive this relationship. The ecological engineering of seawalls is one area where this topic has advanced, albeit not often at scales relev...
Marine microplastics have become a pernicious global pollution issue. As field surveys to determine microplastic abundance in the marine environment and/or biota become more common, it is important to refine collection techniques to minimize contamination of samples. However, most contemporary sampling equipment is fabricated with plastic component...
In the marine environment, greening of grey infrastructure (GGI) is a rapidly growing field that attempts to encourage native marine life to colonize marine artificial structures to enhance biodiversity, thereby promoting ecosystem functioning and hence service provision. By designing multifunctional sea defences, breakwaters, port complexes and of...
Reproduction and early life history are central to understanding the biology and ecology of organisms, however such information is limited for solitary corals. Here, we compared the reproductive traits of the solitary coral Heliofungia actiniformis from different latitudinal locations (Singapore, 1°N and the Philippines, 16°N) and examined their ea...
The successful implementation of coastal eco-engineering strategies, such as retrofitting biodiversity enhancement units onto seawalls, requires scientific, economic, and social inputs. It is important to involve various agencies and local communities to gauge the level of public support, especially when local coastal areas function as public ameni...
Allelopathic chemicals facilitated by the direct contact of macroalgae with corals are potentially an important mechanism mediating coral–macroalgal interactions, but only a few studies have explored their impacts on coral health and microbiomes and the coral’s ability to recover. We conducted a field experiment on an equatorial urbanized reef to a...
Despite increasing research into the effects of microplastics on corals, no study to date has compared this relatively novel pollutant with a well-established stressor such as downwelling sediments. Here, Merulina ampliata coral fragments were exposed to polyethylene terephthalate (PET) and calcium carbonate particles (200-300 μm) at two deposition...
Context
In contrast to marine environments, microplastic pollution in freshwater systems is understudied. Previous research suggests that freshwater macrophytes function as microplastic sinks, which, because they are at the base of food webs, has implications for higher trophic levels.
Aim
This study compares the ability of freshwater plants with...
The intertidal zone is a harsh environment for marine life as conditions are often both extreme and variable. A wide range of sessile organisms are partially or fully emersed (exposed above the water line) during low tide. In the tropics, when corals are emersed, high light and temperature can be detrimental to their survival. To date, there is no...
Characterisation of genomic variation among corals can help uncover variants underlying trait differences and contribute towards genotype prioritisation in coastal restoration projects. For example, there is growing interest in identifying resilient genotypes for transplantation, and to better understand the genetic processes that allow some indivi...
Habitat complexity is positively associated with biodiversity and abundance and is often a focus of habitat restoration programmes, however, the mechanisms underlying these relationships are not yet resolved. In this Perspective, we postulate that reduced predation pressure in complex habitats could contribute to increased prey diversity and abunda...
Anthropogenic sedimentation is a major contributor to the worldwide decline in coral cover. Resuspension of benthic material can exacerbate the threat to corals, but evidence of vertical sediment gradients is limited. Here, we installed sediment traps at 10, 20, 30, 40, and 50 cm above the substrate at three equatorial reef sites for three months a...
Increasing incidence of severe coral bleaching events caused by climate change is contributing to extensive coral losses, shifts in species composition and widespread declines in the physical structure of coral reef ecosystems. With these ongoing changes to coral communities and the concomitant flattening of reef structural complexity, understandin...
Seawalls are important in protecting coastlines from currents, erosion, sea-level rise, and flooding. They are, however, associated with reduced biodiversity, due to their steep orientation, lack of microhabitats, and the materials used in their construction. Hence, there is considerable interest in modifying seawalls to enhance the settlement and...
Southeast Asia is considered to have some of the highest levels of marine plastic pollution in the world. It is therefore vitally important to increase our understanding of the impacts and risks of plastic pollution to marine ecosystems and the essential services they provide to support the development of mitigation measures in the region. An inter...
Coastal cities and their natural environments are vulnerable to the impacts of climate change, especially sea-level rise (SLR). Hard coastal defences play a key role in protecting at-risk urban coastal populations from flooding and erosion, but coastal ecosystems also play important roles in the overall sustainability and resilience of cities and u...
Tropical species are predicted to be among the most vulnerable to climate change as they often live close to their upper limits to thermal tolerance, and in many cases behavioural thermoregulation is required to persist in the thermal extremes of tropical latitudes. In concert with warming temperatures near-shore species are faced with the addition...
The urbanisation and hardening of shorelines is likely to continue in response to coastal population growth and climate change. To mitigate associated ecological impacts, ecological engineering is being increasingly applied to enhance local biodiversity. This includes retrofitting topographically complex tiles or units onto intertidal artificial st...
Giant clam populations in Singapore are endangered due to historical exploitation, habitat loss, and sediment pollution.
Transplanting cultured giant clams onto reefs is a potential conservation strategy. This study examined the growth and survival of three initial size classes (50.0–60.0 mm, 60.1–70.0 mm, >70 mm) of cultured juvenile fluted giant...
Marine urbanisation often results in the proliferation of artificial coastal defences and heavy sedimentation, adversely impacting coral reef systems in tropical coastal cities. Knowledge of how motile organisms, such as reef fish, respond to novel human-made habitats and high sedimentation is limited. Here, we examine the role of sloping granite s...
Crustose coralline algae (CCA) and other encrusting calcifiers drive carbonate production on coral reefs. However, little is known about the rates of growth and calcification of these organisms within degraded turbid reef systems. Here we deployed settlement cards (N = 764) across seven reefs in Singapore for two years to examine spatio-temporal va...
Interactions between corals and macroalgae are important in influencing benthic community structures on coral reefs and have become increasingly common occurrences. However, little is known about their temporal variation as most studies have only documented them from single surveys. To investigate the dynamics of coral–macroalgal interactions, we s...
There is a growing interest in transplanting corals onto the intertidal section of artificial coastal defences (e.g., seawalls) as an ecological engineering strategy to enhance biodiversity on urban shores. However, this inevitably results in exposure to the harsh environmental conditions associated with emersion (aerial exposure). Although the eff...
Decision makers are calling for actionable science to protect coastal ecosystems from adverse impacts. Future sea level rise (SLR) is expected to alter the spatial configuration of coastal habitats and their services. Ensuring conservation efforts are in optimal areas can be achieved using systematic conservation planning, yet plans rarely address...
Fear of predators (‘fear effects’) is an important determinant of foraging decisions by consumers across a range of ecosystems. Group size is one of the main behavioural mechanisms for mitigating fear effects while also providing foraging benefits to group members. Within coral reef ecosystems, fear effects have been shown to influence the feeding...
This study examines phenotypically plastic responses in Pocillopora acuta collected from a highly urbanized reef environment to extreme low-light conditions. While among-species differences in how corals cope with low light are well documented, much less is known about within-species responses. It also remains unclear how extreme low light and prov...
Coastal habitats have faced decades of loss caused by urbanization. Global recognition of the ecosystem services that coastal habitats provide has led to an emphasis on cities to adopt nature-based solutions (NBS). However, a broad assessment of urban areas and their potential to conserve remaining coastal habitat has not been undertaken. Here we a...
Sediment rejection efficiency of five scleractinian corals was studied in situ at the western fringing reef of Pulau Hantu, Singapore. Colonies of five coral species were exposed to two sediment treatments: low (100 g cm −2) and high (200 g cm −2). Clearance was calculated from photographs taken after initial sediment deposition (100% cover on a 50...
Stony corals are promising transplant candidates for the ecological engineering of artificial coastal defences such as seawalls as they attract and host numerous other organisms. However, seawalls are exposed to a wide range of environmental stressors associated with periods of emersion during low tide such as desiccation and changes in salinity, t...
Macroalgal removal is a critical ecosystem function yet few studies have considered its temporal variability, especially on impacted reefs with limited herbivorous fish biodiversity. To address this, we quantified macroalgal removal and mass-standardised bite rates of herbivorous fishes monthly from July 2016 to June 2017 using a series of transpla...
The reefs of Singapore provide an excellent opportunity to study the population dynamics and growth rates of free-living mushroom corals (Fungiidae) under sediment-stressed conditions. Transect surveys at four study sites revealed a total of 11 free-living mushroom coral species—the same 11 species as those found by local studies since the 1980s. T...
Retrofitting microhabitat features is a common ecological engineering technique for enhancing biodiversity and abundance of small, epilithic organisms on artificial shorelines by providing refuge spaces and/or ameliorating abiotic conditions. These features are typically too small to be utilised as refugia by larger, highly motile consumers such as...
Phytoplankton play a fundamental role in marine food webs but are affected by both natural and anthropogenic fluctuations in environmental conditions. Here, to simulate a dynamic coastal environment, we used mesocosms to examine how different salinity levels and suspended solids concentrations (SSCs) impact a natural phytoplankton assemblage collec...
The ability of corals to withstand changes in their surroundings is a critical survival mechanism for coping with environmental stress. While many studies have examined responses of the coral holobiont to stressful conditions, its capacity to reverse responses and recover when the stressor is removed is not well-understood. In this study, we invest...
Concrete is one of the most commonly used materials in the construction of coastal and marine infrastructure despite the well known environmental impacts which include a high carbon footprint and high alkalinity (~pH 13). There is an ongoing discussion regarding the potential positive effects of lowered concrete pH on benthic biodiversity, but this...
Urban coral reefs are regarded as marginal communities that live under localized conditions considered detrimental for coral survival, such as high sediment load. They are also impacted by global environmental changes, especially increases in sea surface temperatures. These conditions can cause sub-optimal performance and may lead to dissociation o...
Globally, many coral reefs have fallen into negative carbonate budget states, where biological erosion exceeds carbonate production. The compounding effects of urbanization and climate change have caused reductions in coral cover and shifts in community composition that may limit the ability of reefs to maintain rates of vertical accretion in line...
Green spaces and agronomy have long been used in terrestrial urban environments to help mitigate the negative effects of urbanization on social-ecological systems. However, they represent an unexplored frontier in marine urban environments, which are also central to human–environment interactions in coastal cities. We evaluated the feasibility and...
The coastal waters of Singapore support coral reefs that are biodiverse but characterized by high turbidity and sedimentation. Here, we used internal transcribed spacer two (ITS2) amplicon sequencing to investigate the Symbiodiniaceae communities associated with this marginal reef system, as turbid reefs may serve as potential refugia from future t...
Seagrasses cope with excess irradiance using a suit of photoprotective mechanisms, however, Halophila species are the only seagrasses known to exhibit chloroplast avoidance movement. Here we examined this phenomenon together with concurrent change in photosynthetic and leaf optical properties in H. ovalis and H. decipiens. Although co-existing, the...
Urban shorelines undergo substantial hydrodynamic changes as a result of coastal engineering and shoreline armouring that lead to major shifts in sedimentation, turbidity, and other factors. These changes often coincide with major shifts in the composition and distribution of marine biota, however, rarely are hydrodynamic-mediated factors confirmed...
Various crab taxa are known to use their external colouration as visual courtship signals. Early research on the mangrove crab Parasesarma peninsulare Shahdadi et al., 2018 indicated a potential role for its bright blue-green facial bands, which are highly conspicuous against mangrove mud, in sexual signalling. To advance this work, we conducted ex...
Microplastic accumulation on marine macrophytes, such as macroalgae and seagrasses, is a potentially critical but overlooked pathway by which microplastics enter the marine food web. Despite the possible significance of this pathway, few studies have examined the presence of microplastics on macrophytes found in situ. We quantified the density of m...
Copepod swimming behavior is governed by chemical and hydro-mechanical cues. The environment of copepods, however, is frequently impacted by anthropogenic activities, in particular increased levels of suspended sediment due to coastal development. To better understand the effects of sediments on copepod behavior, we used video recordings to documen...
Competitive interactions between corals and macroalgae play an important role in determining benthic community structure on coral reefs. While it is known that macroalgae may negatively affect corals, the relative influence of contact- versus water-mediated macroalgal interactions on corals – such as via an influence on coral-associated microbiomes...
The exchange of genetic material between seagrass meadows is fundamental to maintaining their genetic diversity and, consequently, resilience against stressors and disturbances. Increasingly, biophysical models are being used to predict the movement and dispersal of seagrass propagules (i.e. fruits, seeds, vegetative fragments) to better understand...
Quantifying contributors to light attenuation is useful for the management of seagrass meadows. Epiphytic growth on seagrasses can lead to diminished light for the host plant, impairing photosynthesis and growth. Here, we quantify the contributions of the water column and epiphytic load to light attenuation in a Cymodocea rotundata meadow at Chek J...
Seagrasses need to be resilient if they are to persist in the long term. Being able to build up a dormant seed bank in sediments is a key strategy that some species employ to regenerate from large-scale degradation. Much of the research on seed banks has focussed on temperate species, and little is known regarding the status of seed banks in tropic...
In the field of marine biology-inspired robotics, anguilliform locomotion, as one of the most common underwater propulsion types, has been widely studied and implemented in many robot prototypes. Most of these robots consisted of rigid parts, and they were able to generate smooth sine waves along the robot body using a great number of rigid segment...
This paper examines the responses of the fluted giant clam Tridacna squamosa pediveligers to elevated temperature and reduced light levels. In a light reduction experiment, a total of 104,000 T. squamosa pediveligers were exposed to four different levels of shading for approximately one month. The most heavily shaded treatment, at 0.4% of ambient l...
Non-consumptive fear effects are an important determinant of foraging decisions by consumers across a range of ecosystems. However, how fear effects associated with the presence of predators interact with those associated with habitat structure remain unclear. Here, we used predator fish models (Plectropomus leopardus) and experimental patches of t...
Human population density within 100 km of the sea is approximately three times higher than the global average. People in this zone are concentrated in coastal cities that are hubs for transport and trade – which transform the marine environment. Here, we review the impacts of three interacting drivers of marine urbanization (resource exploitation,...
Human population growth and accelerating coastal development have been the drivers for unprecedented construction of artificial structures along shorelines globally. Construction has been recently amplified by societal responses to reduce flood and erosion risks from rising sea levels and more extreme storms resulting from climate change. Such stru...
Marine environments abound with opportunities to discover new species of fungi even in relatively well-studied ecosystems such as coral reefs. Here, we investigated the fungal communities associated with the canopy forming macroalga Sargassum ilicifolium(Turner) C. Argardh (1820) in Singapore. We collected eight S. ilicifolium thalli from each of e...
Human population growth and accelerating coastal development have been the drivers for unprecedented construction of artificial structures along shorelines globally. Construction has been recently amplified by societal responses to reduce flood and erosion risks from rising sea levels and more extreme storms resulting from climate change. Such stru...