I am an ecologist in the Department of Ecology and Evolutionary Biology at Brown University. My research is focused on understanding how the diversity, distribution, and abundance of plants and animals drive the emergent properties of coastal ecosystems. The land-sea interface is a rich and productive region, but is changing at an accelerating rate due to globally important factors including overexploitation of resources, species invasions, extinctions, and habitat degradation. This makes coastal ecosystems both a conservation priority and a model system for investigating human impacts on the natural world. I employ a combination of field experiments and large-scale observations to develop a practical understanding of coastal ecosystems that is rooted in both natural history observation and ecological theory. I have 3 areas of ongoing research:
How are coastal plant communities affected by the overexploitation of consumers?
Salt marshes in the Northeastern US are among the most recent coastal habitats to suffer rapid ecosystem collapse. Marsh vegetation is being lost at an accelerating rate, doubling in the past decade, and resulting in a unvegetated moonscape prone to erosion. Through large-scale surveys, historical reconstruction of marsh landscapes, and field experiments, my research has identified localized overexploitation of top predators as the trigger of vegetation loss because there are insufficient predators to control populations of herbivorous crabs. My previous work in rocky habitats found that even marginal increases in herbivore abundances can tip the balance among plant species and have profound and unexpected impacts on primary productivity.
How does habitat modification by plants affect patterns of biodiversity and species invasion?
Some species have a pivotal role in community composition and ecosystem properties because they engineer their environment through habitat modification. I found that such foundation species can work synergistically through a “facilitation cascade” in which they shield other organisms from harsh environmental conditions. Through a series of surveys and experiments that included mimics of foundation species and manipulations of substrate instability and solar stress, I found that a dominant beach grass facilitated a secondary foundation species, which in turn had cascading benefits for the abundance and diversity of native invertebrates and algae, and invasive crabs as well. By demonstrating agreement between small-scale experiments and large-scale observation when the role of facilitation is incorporated, my work dispels the “invasion paradox” which had previously hampered the ability of experimentalists and observational ecologists to advance our understanding of species invasions.
How does habitat degradation affect ecosystem function?
Studies of habitat degradation have generally focused on the negative impacts of anthropogenic disturbance. Coastal hypoxia is an anthropogenic disturbance that is accelerating worldwide due to the combined effects of eutrophication (increased nutrients) and climate change, and is generally characterized by mass-mortality of marine life and resultant “dead zones”. I found that low-oxygen conditions can actually enhance the abundance of economically valuable shellfish by causing mobile predators to flee stressful hypoxia areas, leaving sufficiently hypoxia-tolerant clams with a predation refuge. Notably, I found that these apparent benefits of hypoxia mask downward trends associated with degraded water quality including overall declines in biodiversity and the loss of ecosystem services such as water filtration. My organismal research revealed that the discrepancy among marine species in their tolerance and ability to exploit degraded conditions are due to metabolic differences.
Teaching and mentoring are valuable aspects of my professional activities. I encourage student participation in the scientific process in and out of the classroom, and have mentored undergraduates through summer internships and published theses. The following are outlines of my currently and recently courses:
Coastal Ecology and Conservation (Environmental Studies 0455, Brown University)
This intermediate-level course will enable to students to master fundamental ecological concepts and understand how this knowledge can be used to inform coastal conservation and management. Through case studies and a multi-day field trip to Cape Cod, students will develop scientific skills and experience the challenges and opportunities of coastal conservation science. Co-taught with Dr. Mark Bertness.
Marine Ecology (Biology 1440, Brown University)
The objective of this class is to examine the factors dictating the abundance and distribution of marine organisms and the ways that marine organisms cope with their physical and biotic environments. To accomplish this, students will read and critique current literature. This will introduce students to most important topics and problems in marine ecology. Students will also initiate final projects through multi-day field trips to the Sapelo Island, GA to examine the importance of foundation species for the abundance and distribution patterns of barrier island organisms, and to Prudence Island, RI to investigate heavily invaded beach plant communities.
Invertebrate Zoology (Biology 0410, Brown University)
This class surveys the major taxonomic groups of invertebrate and their phylogenic relationships. Each group is defined by its major characteristics in terms of evolutionary trajectory, adaptations, and ecological context. The class is comprised of weekly lectures and hands-on laboratory activities with live and preserved specimens, and two field trips to coastal research reserves.
Marine Invertebrate Zoology (Biology 5503, Northeastern University)
This class develops a practical knowledge of invertebrate natural history and evolutionary relationships, with an emphasis on marine taxonomic groups. Attention is given to ecologically and conservation significant species species that Three Seas students will encounter during their field work in the New England, US West Coast, and French Polynesia. The class meets once weekly for a combination of lectures, laboratory exercises, and field activities that take advantage of adjacent intertidal habitats in Nahant, MA.
Tropical Biology (Biology 0190K, Brown University)
The Tropical Biology Freshman Seminar will explore tropical biology and conservation in a seminar. The major goal will be to develop an understanding of the uniqueness of tropical organisms and ecosystems and to examine conservation issues in tropical ecosystems. This will be accomplished through a mixture of lectures, discussions and student presentations. The course will end with a field trip to Belize during winter break to learn first hand about tropical ecosystems. Co-taught with Dr. Mark Bertness.
Tropic Marine Biology (Biology 3660, University of Virginia)
The course is designed to introduce students to the plants and animals found in the marine and terrestrial environments of the Caribbean and to study their adaptations in the context of community ecology. The course takes place primarily on Sal Salvador island in the Bahamas, and will be divided into three components: (1) Prior to departure, a three or four day orientation session in Charlottesville, VA will be used for lectures, discussions and an introduction to field methods. (2) During the first week of the 15 days spent on San Salvador, learning will be directed through lectures, lab work, discussion, readings with an emphasis on visiting representative ecological sites on the island to observe organisms in situ. (3) During the last week on San Salvador, students will conduct independent research projects developed with a faculty mentor. Co-taught with Drs. Fred Diehl and David Smith.
LIST OF PUBLICATIONS
Thomsen, M.S., T. Wernberg, A. H. Altieri, F. Tuya, D. Gulbransen, K. McGlathery, M. Holmer, B.R. Silliman (2010) Habitat cascades: the conceptual context and global relevance of facilitation cascades via habitat formation and modification. Integrative and Comparative Biology 50:158-175. [PDF]
Altieri, A.H., B.K. van Wesenbeeck, M.D. Bertness, and B.R. Silliman (2010) Facilitation cascade explains positive relationship between native biodiversity and invasion success. Ecology 91: 1269-1275. [PDF]
*Selected by the Faculty of 1000 Biology
Bertness, M.D., C. Holdredge, and A.H. Altieri (2009) Substrate mediates consumer control of salt marsh cordgrass on Cape Cod, New England. Ecology 90: 2108-2117. [PDF]
Altieri, A.H, G.C. Trussell, P.J. Ewanchuk, G. Bernatchez, and M.E.S. Bracken (2009) Consumers control diversity and functioning in a natural marine ecosystem. PLoS ONE 4: e5291. [PDF]
Holdredge, C., M.D. Bertness, and A.H. Altieri (2009) Crab herbivory driven die-off of New England salt marshes. Conservation Biology 23: 617-692. [PDF]
Altieri, A.H. (2008) Dead zones enhance key fisheries species by providing predation refuge. Ecology 89: 2808-2818. [PDF]
*Selected for Ecological Society of America’s monthly podcast (Field Talk, 10/08).
Van Wesenbeeck, B.K., C.M. Crain, A.H. Altieri, and M.D. Bertness (2007) Distinct habitat types arise along a continuous hydrodynamic stress gradient due to the interplay of competition and facilitation. Marine Ecology Progress Series 349: 63-71. [PDF]
Altieri, A.H., B.R. Silliman, M.D. Bertness (2007) Hierarchical organization via a facilitation cascade in intertidal cordgrass bed communities. American Naturalist 169: 195-206. [PDF]
Zabin, C.J. and Altieri, A. (2007) A Hawaiian limpet facilitates recruitment of a competitively dominant invasive barnacle. Marine Ecology Progress Series 137: 175-185. [PDF]
Altieri, A.H. (2006) Inducible variation in hypoxia tolerance across the intertidal-subtidal distribution of the blue mussel Mytilus edulis. Marine Ecology Progress Series 325: 295-300. [PDF]
Altieri, A.H. and J.D. Witman (2006) Local extinction of a foundation species in a hypoxic estuary: integrating individuals to ecosystem. Ecology 87: 717-730. [PDF]
Van de Koppel, J., A. H. Altieri, B.R. Silliman, J. F. Bruno, and M. D. Bertness (2006) Scale-dependent interactions and community structure on cobble beaches. Ecology Letters 9: 45-50. [PDF]
Lindsey, E. L., A.H. Altieri, J.D. Witman (2006) Influence of biogenic habitat on the recruitment and distribution of a subtidal xanthid crab. Marine Ecology Progress Series 306: 223-231. [PDF]
Altieri, A.H. (2003) Settlement cues in the locally dispersing temperate cup coral Balanophyllia elegans. Biological Bulletin 204: 241-245. [PDF]
Silliman, B.R., C.A. Layman, and A.H. Altieri (2003) Symbiosis between an alpheid shrimp and a xanthoid crab in salt marshes of mid-Atlantic states, U.S.A. Journal of Crustacean Biology 23: 876-879. [PDF]
(Underline indicates undergraduate author)