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Simon Thrush

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Papers by Simon Thrush

Simplifying the complex: an ‘Ecosystem Principles Approach’ to goods and services management in marine coastal ecosystems

Marine Ecology Progress Series, Jul 28, 2011

The ability to manage complex systems effectively must stem from simplifications of ecological kn... more The ability to manage complex systems effectively must stem from simplifications of ecological knowledge. We present a technique called the 'Ecosystem Principles Approach' (EPA) as a progressive way of incorporating ecology into goods and services assessments. The EPA moves away from the complexity of ecosystem functions and focuses on general ecological principles. These principles more explicitly define key elements of system functioning, are not spatially or temporally confined, and can be utilised in assessment and decision-making processes. When applied to a coastal system in New Zealand, the EPA highlighted that services were primarily dependent on connectivity and that the maintenance of healthy intertidal areas was highly important for system functioning. The approach also demonstrated a separation between locations where ecosystem functions were generated and where services were valued. A high level of multi-functionality and connectivity between goods and services in marine coastal systems suggests services should be managed collectively rather than individually. The strength of the EPA is that it aligns to the principles of 'Ecosystem-Based Management'. This approach demonstrates how ecological information can be simplified into a format that can advise policy and better integrate with management. It highlights the need for greater trans-disciplinary integration of ecology and social science to better understand how human interactions result in critical community shifts and loss of resilience. KEY WORDS: Complexity • Ecosystem-based management • Ecosystem functions • Ecosystem processes • Fundamental principles • Goods and services • Millennium Assessment Resale or republication not permitted without written consent of the publisher Contribution to the Theme Section 'Biodiversity, ecosystems and coastal zone management'

Cross-Scale Variation in Biodiversity-Environment Links Illustrated by Coastal Sandflat Communities

PLOS ONE, Nov 10, 2015

Spatial variation in the composition of communities is the product of many biotic and environment... more Spatial variation in the composition of communities is the product of many biotic and environmental interactions. A neglected factor in the analysis of community distribution patterns is the multi-scale nature of the data, which has implications for understanding ecological processes and the development of conservation and environmental management practice. Drawing on recently established multivariate spatial analyses, we investigate whether including relationships between spatial structure and abiotic variables enable us to better discern patterns of species and communities across scales. Data comprised 1200 macrozoobenthic samples collected over an array of distances (30 cm to 1 km) in three New Zealand harbours, as well as commonly used abiotic variables, such as sediment characteristics and chlorophyll a concentrations, measured at the same scales. Moran's eigenvector mapping was used to extract spatial scales at which communities were structured. Benthic communities, representing primarily bivalves, polychaetes and crustaceans, were spatially structured at four spatial scales, i.e. >100 m, 50-100 m, 50-15 m, and < 15 m. A broad selection of abiotic variables contributed to the large-scale variation, whereas a more limited set explained part of the fine-scale community structure. Across all scales, less than 30% of the variation in spatial structure was captured by our analysis. The large number of species (48) making up the 10 highest species scores based on redundancy analyses illustrate the variability of species-scale associations. Our results emphasise that abiotic variables and biodiversity are related at all scales investigated and stress the importance of assessing the relationship between environmental variables and the abundance and distribution of biological assemblages across a range of different scales.

Terrigenous deposits in coastal marine habitats: influences on sediment geochemistry and behaviour of post-settlement bivalves

Marine Ecology Progress Series, May 14, 2009

Dispersal of post-settlement juvenile macrofauna is widespread in the marine environment, yet the... more Dispersal of post-settlement juvenile macrofauna is widespread in the marine environment, yet the cues used by these organisms to assess substrate suitability are poorly known. We investigated how deposition of fine terrestrial sediments (TS, 0.5 to 1.7 mm thick) affects both the solute concentrations at the sediment -water boundary and the burrowing behaviour of juvenile tellinid bivalves Macomona liliana. To elucidate previously observed gradual reduction in the strength of macrofaunal responses with increasing age of deposits, the effect of TS weathered in the field for 0, 7 and 14 d, and the influence of surface and buried TS layers, were also investigated. Burrowing was significantly reduced in 0 and 7 d old surface TS compared with controls, but there was no effect of buried deposits on M. liliana burrowing, irrespective of sediment age. Microelectrode measurements showed that thin surface TS layers reduced the supply of O 2 to the underlying sediment, raising the position of the vertical [O 2 ] and pH gradients so that most of the gradient was located in the TS layer itself, rather than deeper in the sediment below it. Consequently, the likelihood of juveniles that are active in the near-surface layers being exposed to upward diffusing end products of microbial decomposition was increased. These results suggest a mechanism for the observed negative response of post-settlement M. liliana (and other macrofauna) to TS deposits associated with sedimentation events, and an avenue for further research into potential geochemical cues (especially pH and associated geochemical species).

Modelled broad-scale shifts on seafloor ecosystem functioning due to microplastic effects on bioturbation

Research Square (Research Square), Jun 26, 2023

Many studies have found that microplastic (MP) is increasing in marine sediments and threatening ... more Many studies have found that microplastic (MP) is increasing in marine sediments and threatening benthic species' health. However, the links to changes in ecosystem function have yet to be made. The study investigates this linkage between MP contamination and ecosystem functions using experimental observations to parametrize bioturbation coefficients (D b ) in a simplified transport-reaction model. Bioturbating species play an essential role in regulating nutrient cycling in marine sediments, and their interaction with MP can be upscaled to an ecological level. In the MP-contaminated sediment, organic matter accumulates in the oxic sediment zone leading to a cascading effect that stimulates aerobic respiration by 18%. The composition of bioturbators modulates this shift in the ecosystem functioning. Maldanid worms, typically classified as deep burrowing upwardconveyor belt feeders, became less active, and the D b was reduced by 30% with the additive of 0.02 g MP cm -2 at surface sediment. The tellinid bivalve, usually classified as a mediumdepth burrower, surface deposit feeder, and bioirrigator, retained its particle mixing behaviour in MP-contaminated systems. This study provides a mechanistic insight into the impact of MP and indicates that the functional role of bioturbating species should be involved in assessing the global impact of MP.

Spatial heterogeneity in subtidal gravel generated by the pit-digging activities of Cancer pagurus

Marine Ecology Progress Series, 1986

In a coarse gravelly substratum exposed to high current velocities the crab Cancer pagurus was ob... more In a coarse gravelly substratum exposed to high current velocities the crab Cancer pagurus was observed to dig pits, approximately 30 cm in diameter and 10 cm deep. Experiments were conducted to identify macrobenthic recolonization processes and differences in abundance between pits and unmanipulated areas. Surveys of the abundance of recently dug pits indicate a frequency of approximately 9 pits 100 mA2. Analysis of species abundances in artificial pits at various times after construction revealed colonizing species to be highly variable. In a second experiment statistically significant differences in the abundances of various species were found between artificial pits and adjacent unmanipulated sediment, but trends in the data were not consistent between experiments. Generally, macrofaunal recolonization processes were haphazard. These results are contrasted with initial recolonization processes in soft sediments. The mobllity and large particle size of the sediment are considered to be important in precluding predictable recoloruzation patterns.

Macrobenthic colonisation of disturbances on an intertidal sandflat:the influence of season and buried algae

Marine Ecology Progress Series, 1999

This study examines whether macrofaunal colonisation differs seasonally in an intertidal sandflat... more This study examines whether macrofaunal colonisation differs seasonally in an intertidal sandflat. Frozen cores were placed in the sandflat within each season and colonisation of these cores was followed for 50 d. This study shows a previously untested effect of buried algal mats on colonisation. A change in the sediment organic content can increase or decrease macrofaunal densities. Community colonisation rates of defaunated plugs were slower in winter compared to summer because of the higher numbers of rare macrofauna in winter. Community colonisation of plugs with algal additions were also dependent on the seasonally varying response of the coroph~id amphipod Paracorophium excavatum, the most abundant species in this community. The strongest effect of the experiments was linked to critical densities of P. excavatum, irrespective of season. A mechanism for this llnkage is suggested. This study also emphasises the importance of post-settlement movement as the mechanism by which most species on this sandflat colonised in either season.

Scale- and intensity-dependent disturbance determines the magnitude of opportunistic response

Journal of Experimental Marine Biology and Ecology, Mar 1, 2006

... The macrofaunal community is dominated by large bioturbating lugworms (Arenicola marina), coc... more

Scaling-up ecosystem functions of coastal heterogeneous sediments: testing practices using high resolution data

Landscape Ecology, Apr 27, 2022

underestimated denitrification (81.9% less) but overestimated NH 4 + efflux and organic matter de... more underestimated denitrification (81.9% less) but overestimated NH 4 + efflux and organic matter degradation (2594.1 and 14,879.9% more). Kriging produced more accurate results and the predicted functions only differed from the estimated values by 14.7, 29.4 and 3.9% respectively. Conclusions Our work shows that the choice of the scaling method is crucial in estimating intertidal soft sediment functions and highlights the need for empirical and theoretical models that link ecosystem functioning to biological attributes that can be measured remotely over large areas. Integrating measures of heterogeneity through the spatial structure of the data leads to outcomes that are more realistic and relevant to resource management.

Multi-scale data on intertidal macrobenthic biodiversity and environmental features in three New Zealand harbours

Earth System Science Data, Feb 10, 2020

Understanding how the plants and animals that live in the sea floor vary in their spatial pattern... more Understanding how the plants and animals that live in the sea floor vary in their spatial patterns of diversity and abundance is fundamental to gaining insight into the role of biodiversity in maintaining ecosystem functioning in coastal ecosystems, as well as advancing the modelling of species distributions under realistic assumptions. Yet, it is virtually unknown how the relationships between abundance patterns and different biotic and environmental processes change depending on spatial scales, which is mainly due to a lack of data. Within the project Spatial Organization of Species Distributions: Hierarchical and Scale-Dependent Patterns and Processes in Coastal Seascapes at the National Institute for Water and Atmospheric Research (NIWA) in New Zealand we collected multi-scale and high-resolution data on macrobenthic biodiversity. We found 146 species dominated by bivalves, polychaetes, and crustaceans ( > 500 µm) that live hidden in marine sandflats and collected point measurements of important environmental variables (sediment grain-size distributions, chlorophyll a concentration, organic content, and visible sandflat parameters) in three large intertidal harbours (Kaipara, Tauranga, and Manukau). In each harbour we sampled 400 points for macrobenthic community composition and abundances, as well as the full set of environmental variables. Using an elaborate sampling design, we were able to cover scales from 30 cm to a maximal extent of 1 km.

Enhancing multiple scales of seafloor biodiversity with mussel restoration

Scientific Reports, 2022

Restoration projects are underway internationally in response to global declines in shellfish bed... more Restoration projects are underway internationally in response to global declines in shellfish beds. As diverse biological assemblages underpin a variety of ecosystem services, understanding broader changes in biodiversity associated with mussel restoration becomes increasingly valuable to scientists and restoration practitioners. Studies generally show bivalve beds increase species richness and abundance, but results are scale-dependent and conditional on the mobility of specific communities observed. We examined biodiversity at multiple scales to determine how communities with varying levels of mobility are influenced by subtidal mussel restoration. Significant changes in assemblage structure were observed in both mobile fish and epifaunal communities, with enhanced species richness and total abundance of associated individuals. In contrast, we observed site-dependent effects of bivalve restoration on macrofaunal community structure and composition, with sheltered, harbour mussel b...

A multi-scale framework for the automated surveying of the Whangateau estuary using off-the-shelf equipment

2017 International Conference on Image and Vision Computing New Zealand (IVCNZ), 2017

We propose here a first attempt at meta-scale mapping for long-term marine ecosystem management b... more We propose here a first attempt at meta-scale mapping for long-term marine ecosystem management by prototyping, advancing and applying an intelligent vision system to map the marine estate. We will offer a first glimpse at data collection that crosses scales using IR, colour and depth imagery data from the millimetric to the metric scale. We used proprietary hardware and algorithms to look at the activity of Polychaete worms (a recognized indicator of a healthy estuary environment) across spatial, temporal and physical scales, from micro to macro level. While our estimation of worm counts correlated weakly with manual expert ground truth, our system allowed a scaling of worm activity at various levels, which is a first attempt at marine ecosystem meta-scale mapping capabilities. The field investigations took place on a stretch of intertidal area in the Auckland Region near the Leigh Marine Laboratory, which allows easy access to a typical marine ecosystem, ensures natural illumination, and is rich in complex interactions in the underwater biotic/abiotic interface.

A call to evaluate Plastic’s impacts on marine benthic ecosystem interaction networks

Environmental Pollution, 2021

Plastic pollution continues to seep into natural and pristine habitats. Emerging laboratory-based... more Plastic pollution continues to seep into natural and pristine habitats. Emerging laboratory-based research has evoked concern regarding plastic's impact on ecosystem structure and function, the essence of the ecosystem services that supports our life, wellbeing, and economy. These impacts have yet to be observed in nature where complex ecosystem interaction networks are enveloped in environmental physical and chemical dynamics. Specifically, there is concern that environmental impacts of plastics reach beyond toxicity and into ecosystem processes such as primary production, respiration, carbon and nutrient cycling, filtration, bioturbation, and bioirrigation. Plastics are popularly regarded as recalcitrant carbon molecules, although they have not been fully assessed as such. We hypothesize that plastics can take on similar roles as natural recalcitrant carbon (i.e., lignin and humic substances) in carbon cycling and associated biogeochemistry. In this paper, we review the current knowledge of the impacts of plastic pollution on marine, benthic ecosystem function. We argue for research advancement through (1) employing field experiments, (2) evaluating ecological network disturbances by plastic, and (3) assessing the role of plastics (i.e., a carbon-based molecule) in carbon cycling at local and global scales.

Environmental predictors of sediment denitrification rates within restored green-lipped mussel Perna canaliculus beds

Marine Ecology Progress Series, 2021

Benthic processes in coastal marine environments can enhance the natural removal of bioreactive n... more Benthic processes in coastal marine environments can enhance the natural removal of bioreactive nitrogen through denitrification (DNF), a valuable ecosystem service as nutrient over-enrichment intensifies globally. Enhancing ecosystem services is an important justification for restoring coastal ecosystems, and while it is known that epifaunal bivalves (oysters or mussels) are capable of influencing nitrogen cycling, empirical measurement of the role of particular species across a range of environmental conditions is missing. Bivalves within shellfish beds are not uniformly distributed and thus clumps and empty patches within restored beds may differentially impact DNF given the importance of local biogeochemistry. This study reports DNF and respiration rates in 4 restored beds that vary in sediment composition, while identifying which ecological and biogeochemical factors best explain the observed variability in measured fluxes. We deployed benthic chambers in sediments with and wit...

Effects of Polyester Microfibers on Microphytobenthos and Sediment-Dwelling Infauna

Environmental Science & Technology, 2020

Microplastics are accumulating in coastal soft sediments, the majority of which are fibres. Despi... more Microplastics are accumulating in coastal soft sediments, the majority of which are fibres. Despite this, little is known about the potential ecological effects of fibrous material on functionally important benthic organisms. For instance, the microphytobenthos (MPB) and deposit-feeding bivalves which are critical for soft sediment ecosystem functions such as nutrient cycling. Red polyester microfibers (1.8 ± 0.9mm) were added at varying concentrations (0% -XX% DW sediment) to the surface 1cm of sediment in the chambers. The effects of increasing microfiber concentrations on microphytobenthic (MPB) biomass (chl a) and composition (fatty acid (FA) biomarkers) were evaluated after a total exposure period of XX days. Half the chambers were exposed to a 12 h light/dark cycle, to allow photosynthesis to occur, while the remaining

Old Tools, New Ways of Using Them: Harnessing Expert Opinions to Plan for Surprise in Marine Socio-Ecological Systems

Frontiers in Marine Science, 2019

With globally accelerating rates of environmental disturbance, coastal marine ecosystems are incr... more With globally accelerating rates of environmental disturbance, coastal marine ecosystems are increasingly prone to non-linear regime shifts that result in a loss of ecosystem function and services. A lack of early-detection methods, and an over reliance on limits-based approaches means that these tipping points manifest as surprises. Consequently, marine ecosystems are notoriously difficult to manage, and scientists, managers, and policy makers are paralyzed in a spiral of ecosystem degradation. This paralysis is caused by the inherent need to quantify the risk and uncertainty that surrounds every decision. While progress toward forecasting tipping points is ongoing and important, an interim approach is desperately needed to enable scientists to make recommendations that are credible and defensible in the face of deep uncertainty. We discuss how current tools for developing risk assessments and scenario planning, coupled with expert opinions, can be adapted to bridge gaps in quantitative data, enabling scientists and managers to prepare for many plausible futures. We argue that these tools are currently underutilized in a marine cumulative effects context but offer a way to inform decisions in the interim while predictive models and early warning signals remain imperfect. This approach will require redefining the way we think about managing for ecological surprise to include actions that not only limit drivers of tipping points but increase socio-ecological resilience to yield satisfactory outcomes under multiple possible futures that are inherently uncertain.

Benthic responses to an Antarctic regime shift: food particle size and recruitment biology

Ecological Applications, 2019

Polar ecosystems are bellwether indicators of climate change and offer insights into ecological r... more Polar ecosystems are bellwether indicators of climate change and offer insights into ecological resilience. In this study, we describe contrasting responses to an apparent regime shift of two very different benthic communities in McMurdo Sound, Antarctica. We compared species‐specific patterns of benthic invertebrate abundance and size between the west (low productivity) and east (higher productivity) sides of McMurdo Sound across multiple decades (1960s–2010) to depths of 60 m. We present possible factors associated with the observed changes. A massive and unprecedented shift in sponge recruitment and growth on artificial substrata observed between the 1980s and 2010 contrasts with lack of dramatic sponge settlement and growth on natural substrata, emphasizing poorly understood sponge recruitment biology. We present observations of changes in populations of sponges, bryozoans, bivalves, and deposit‐feeding invertebrates in the natural communities on both sides of the sound. Scienti...

Macrofaunal Functional Diversity Provides Resilience to Nutrient Enrichment in Coastal Sediments

Ecosystems, 2017

The degradation of ecosystems is often associated with losses of large organisms and the concomit... more The degradation of ecosystems is often associated with losses of large organisms and the concomitant losses of the ecological functions they mediate. Conversely, the resilience of ecosystems to stress is strongly influenced by faunal communities and their impacts on processes. Denitrification in coastal sediments is a process that may provide ecosystem resilience to eutrophication by removing excess bioavailable nitrogen. Here, we conducted a large-scale field experiment to test the effect of macrofaunal community composition on denitrification in response to two levels of nutrient enrichment at 28 sites across a biologically heterogeneous sandflat. After 7 weeks of enrichment, we measured denitrification enzyme activity (DEA) along with benthic macrofaunal community composition and environmental variables. We normalised treatment site specific DEA values by those in ambient sediments (DEA CN ) to reveal the underlying response across the heterogeneous landscape. Nutrient enrichment caused reductions in DEA CN as well as functional changes in the community; these were both more pronounced

Surprising episodic recruitment and growth of Antarctic sponges: Implications for ecological resilience

Journal of Experimental Marine Biology and Ecology, 2016

Sponges are the most conspicuous component of the Antarctic benthic ecosystem, a system under str... more Sponges are the most conspicuous component of the Antarctic benthic ecosystem, a system under stress both from climate change and fishing activities. Observations over four decades are compiled and reveal extremely episodic sponge recruitmentand growth.Recruitment occurred under different oceanographic conditions on both sides of McMurdo Sound. Most of the sponges appear to have recruited in the late 1990s-2000. Observations from 2000 to 2010follow thirty years of relative stasis with very little sponge recruitment or growth followed by a general pattern of recruitment by some forty species of sponges. That there was almost no recruitment observed on natural substrata emphasizes the contrast between potential and realized recruitment. This unique data set was derived from a region noted for physical stasis,but theepisodic ecological phenomena highlightthe importance of rare events. Against a background of intermittent food resources and the low metabolic costs of stasis, understanding the causes of irregular larval supply, dispersal processes, recruitment success and survivorship becomes critical to predicting ecosystem dynamics and resilience in response to increasing environmental change. Our time-series emphasizes that long-term data collection is essential for meaningful forecasts about environmental change in the unique benthic ecosystems of the Antarctic shelf.

Rapid organic matter assay of organic matter degradation across depth gradients within marine sediments

Methods in Ecology and Evolution, 2017

1. Methods to quickly measure organic matter degradation have been well developed for terrestrial... more 1. Methods to quickly measure organic matter degradation have been well developed for terrestrial and freshwater ecosystems. However, these methods have not been adapted to marine environments. Current methods of assessing organic matter degradation in marine ecosystems are costly, difficult to relate across spatial scales and rarely include sediment depth components to account for redox effects and subsurface macrofaunal activity. 2. We developed a method which is cost effective and time efficient to directly measure rates of organic matter degradation across vertical and horizontal spatial scales in marine sediments. This rapid organic matter assay (ROMA), utilizes a simple design consisting of an acrylic plate with a series of machined wells (0.9 ml) filled with carbon rich substrate. Substrate can be easily adapted to any carbon source by simply modifying the recipe. The plates are deployed with minimal disturbance to the sediment surface and subsurface stratification. Once collected, the resulting change in carbon substrate volume is equated to organic matter degradation. 3. Rapid organic matter assay was shown to be a useful tool in comparing organic matter degradation across sediment redox potentials, habitats within an estuary, and similar habitats across different estuaries. Here, we demonstrate its utility, versatility, and ease of use across a variety of habitats and environments. 4. Rapid organic matter assay is an effective assay for in situ, whole community (micro, meio and macrofauna) organic matter degradation across a myriad of habitats. This supports intensive spatial and temporal analysis that are costly and logistically difficult with current methods. Because it is simple, cost effective, and adaptable, it is an ideal candidate for a standard method to measure organic matter degradation rates in estuaries globally. estuarine habitats, macrofauna activity, marine habitats, organic matter degradation Carbon quality and quantity are important regulatory factors of physical, biological and chemical processes in any ecosystem . Carbon sequestration and consumption/degradation rates both within and between systems are crucial ecosystem functions. Multiple methods have been developed for measuring organic matter degradation, but none of these methods are currently suited to measure rates across vertical and horizontal gradients in marine sediments, are cost effective, and readily available.

Tracking environmental stress gradients using three biotic integrity indices: Advantages of a locally-developed traits-based approach

Ecological Indicators, Nov 1, 2013

Estuarine and coastal ecosystems are productive and functionally diverse areas that provide a wid... more Estuarine and coastal ecosystems are productive and functionally diverse areas that provide a wide range of societal benefits. Along with human exploitative uses comes an array of anthropogenic disturbances that can affect ecological integrity, including changes to the composition and resilience of benthic macroinvertebrate communities. To understand the responses of ecological communities to anthropogenic disturbance and to manage and mitigate effects, indices for assessing the ecological integrity of estuarine and coastal waters have proliferated worldwide. Using data from 84 intertidal sites in Auckland, New Zealand, we evaluated the suitability of two widely used measures of ecological integrity that were developed in USA and Europe, respectively: the Benthic Index of Biotic Integrity (B-IBI) and the AZTI's Marine Biotic Index (AMBI). We then developed a local index based on macrofaunal traits and verified its utility using independent data from >100 additional sites. The local traits based index (TBI), constructed from the richness of macrofaunal taxa in seven functional groups, responded to changes in sediment mud percentage and heavy metal contaminant concentration gradients below international guidelines. The TBI performed better than the indices developed overseas, probably because they were designed to track organic enrichment and hypoxia, which are not the predominant stressors in New Zealand at present. The TBI successfully tracked the stressors that were the most relevant locally and indicated the relative levels of within-group taxonomic richness at various sites. As within-group richness is a component of functional redundancy and ecological resilience, the TBI offers a trifecta of simplicity, robustness and meaningfulness that will facilitate management.