Post-doctoral fellow
Current Research
I’m interested in how effects of anthropogenic stressors on species interactions can lead to unforeseen changes in community structure and ecosystem function. In the northwest Atlantic, increasing ocean temperature associated with climate change enhanced the negative interaction between an invasive, epiphytic bryozoan (Membranipora membranacea) and native seaweeds, resulting in a dramatic regime shift from highly productive kelp bed ecosystems to less productive communities dominated by turf algae. My PhD research involved quantifying the effects of organismal and environmental factors on demographic rates (e.g. fecundity, mortality) and life history processes (e.g. larval settlement behavior) of this ecologically significant invasive bryozoan and incorporated this information into a predictive population model for M. membranacea in its invaded habitat off the coast of Nova Scotia.I used this model to project the bryozoan population under near-future climate scenarios to examine the cumulative impacts of species invasion and climate change on subtidal ecosystems in the northwest Atlantic.
As a postdoctoral fellow in the Metaxas lab I worked in collaboration with Fisheries and Oceans Canada to combine data on sea surface temperature records and corresponding presence/absence and abundance data for M. membranacea collated from multiple government and academic sources throughout the northwest Atlantic. I used these data to examine the relative roles of temperature and available kelp substrate in limiting population outbreaks of the bryozoan at its current invasive northern range limit. Surprisingly, we found that colder temperatures do not appear to be limiting the northward spread of this invasive species in the northwest Atlantic. These results are particularly relevant with respect to the potential spread of the bryozoan into the northeastern Canadian Arctic where laminarian kelps are widespread.
My current postdoctoral research addresses impacts of natural and anthropogenic stressors of different scales and magnitudes on coral reefs in the Solomon Islands. Specifically, I am examining how global stressors (e.g. ocean warming), local stressors (e.g. overfishing, pollution, earthquakes/Tsunamis), local conservation efforts (e.g. protected areas, eradication of Crown-of-thorns starfish) and their interactions affect local scale variation in the diversify, structural complexity, and overall health of coral reefs across a range of reefs with different disturbance histories in the Solomon Islands.
Research grants
Ocean Frontier Institute Seed Fund, Using kelp bed refuges to identify drivers of ecosystem resistance to the combined impacts of climate change and invasive species. PI: D. Denley. (1 year) $14,035
Scholarships and Awards
Level 2 Izaak Walton Killam Predoctoral Scholarship (2015-2018)
NSERC Postgraduate Scholarship – Doctoral Program (2015-2018)
Nova Scotia Research and Innovation Graduate Scholarship – Doctoral Level (2014-2018)
NSERC Undergraduate Student Research Award, Queen’s University (2011)
NSERC Undergraduate Student Research Award, Queen’s University (2010)
Publications
Denley D, Metaxas A, Simard N (2019) Ocean temperature does not limit the establishment and rate of secondary spread of an ecologically significant invasive bryozoan in the northwest Atlantic. Aquatic Invasions (in press)
Denley D, Metaxas A, Fennel K (2019) Community composition influences the population growth and ecological impact of invasive species in response to climate change. Oecologia. https://doi.org/10.1007/s00442-018-04334-4
Denley D, Metaxas A (2017) Lack of substrate specificity contributes to invasion success and persistence of Membranipora membranacea in the northwest Atlantic. Marine Ecology Progress Series. doi:10.3354/meps12287
Denley D, Metaxas A (2017) Effects of intrinsic and extrinsic factors on reproduction of an ecologically significant invasive bryozoan:implications for invasion success. Marine Biology 164:145. doi:10.1007/s00227-017-3172-3
Denley D, Metaxas A (2016) Quantifying mortality of modular organisms: a comparison of partial and whole colony mortality in a colonial bryozoan. Ecosphere 7(10):e01483. 10.1002/ecs2.1483
Denley D, Metaxas A (2015) Recovery capacity of the invasive colonial bryozoan Membranipora membranacea (Linnaeus) from damage: effects of temperature, location, and magnitude of damage. Marine Biology 162: 1769-1778
Denley D, Metaxas A, and Short J (2014) Selective settlement by larvae of Membranipora membranacea and Electra pilosa (Ectoprocta) along kelp blades in Nova Scotia, Canada. Aquatic Biology 21: 47-56
Recent presentations
Denley D (2019) Predicting ecological impacts of invasive species under future climate conditions. Departmental Seminar, April 9th, 2019. Department of Oceanography, Dalhousie University, Halifax, NS Canada
Denley D, Metaxas A, Fennel K (2018) Climate change intensifies negative impacts of an invasive bryozoan on kelp bed ecosystems in the northwest Atlantic. World Conference on Marine Biodiversity. Montreal, QC Canada
Denley D, Metaxas A (2017) New house, new rules: life-history strategies can enhance invasion success of introduced species. Canadian Society for Ecology and Evolution Meeting. Victoria, BC Canada
Denley D, Metaxas A (2016) Mortality of the invasive, colonial bryozoan Membranipora membranacea in the NW Atlantic: the effect of temperature on seasonal colony senescence. Benthic Ecology Meeting. Portland, ME USA
Denley D, Metaxas A (2015) The relative effects of intrinsic and external factors on mortality of the invasive colonial bryozoan Membranipora membranacea. Atlantic Canada Coastal and Estuarine Science Society. St. Andrews, NB Canada
Denley D, Metaxas A (2014) Measuring mortality of the colonial invasive bryozoan Membranipora membranacea: the effect of temperature on partial colony mortality and regeneration. Atlantic Canada Coastal and Estuarine Science Society. Halifax, NS Canada
Denley D, Metaxas A (2014) Quantifying mortality of the colonial invasive bryozoan Membranipora membranacea: the effect of temperature on colony senescence and regeneration. Benthic Ecology Meeting. Jacksonville, FL USA
Additional contributions
Denley D (2015) The regenerative capacity of colonial organisms: an age-old dilemma – Estimating mortality of an invasive bryozoan that is capable of rapid growth and regeneration. Current Tides, Dalhousie Oceanography Research Magazine 2: 16-19
Marine Benthic Ecology and conservation 