Advances in seascape ecology: applying landscape metrics to marine sys - PDF document

NRS 534 Term Paper BJC Fuller / Advances in seascape ecology: applying landscape metrics to marine systems 1 ( 5 ) Ecol Fragmented Landscapes / April 2013 © 2013 (REV 118 ) 20130429 What is seascape ecology? Landscape ecology is a relatively new, multidisc i- plinary field which studies the relationship between ecological functions and spatial patterns (Boström e t al. 2012, Pittman et al. 2011, We d ding inform management practices in terrestrial systems (Pittman et al. 2011). Several important tools , models, and methods of analysis have emerged which advance our underst an d ing of the influence of ge o graphic heterogeneity on the health and sustainability of ecosystems on several scales (Pittman et al. 2011, Wedding et al. 2011). Genera l ly, these metrics assess three fundamental landscape properties: 1) composition, the di versity of patch types; 2) configuration, the arrang e ment complexity of that arrangement (We d ding et al. 2011). While these tools have been developed for and applied in terrestrial systems for nearly 50 years (Pittman et al. 2011), their use in describing spatial patterns in marine context s has only recently emerged , prompting the analogous term se a scapes . This newest branch of landscape ecology treats physical characteristics of marine env i ronments, including geographic and chemical properties, as fundamentally land scape - like patterns which can be correlated with the ecology, life - history, and biod i versity of species in those ecosystems. The complex geographic heterogen e ity that exists on land does not end Mt the wMter’s edge; geophy s ical processes give rise to incredibly diverse coastal environments which support rich species assemblages in both familiar and unique ways. We know that aquatic environments offer special mechanisms for enhancing patc h conne c- tivity and maintaining community structure, and these factors are crucial for sustaining the ecolog i- cal integrity of these systems from multiple perspectives. Some of the most commonly g nized marine spatial patters include the patch mosaics of mangroves, coral reefs, seagrass beds, and tidal marshes, and the zonation of rocky shore and salt marsh biota (Pittman et al. 2011, Boström et al. 2012). Additionally, seascapes may not necessar i ly refer to any particular physical geography of the under water landscape, but can NEWS & VIEWS NRS 534 Term Paper BJC Fuller / Advances in seascape ecology: applying landscape metrics to marine systems 2 ( 5 ) Ecol Fragmented Landscapes / April 2013 © 2013 (REV 118 ) 20130429 also be used to describe variation in chemical composition throug h out the water column. These chemicMl ‘lMn d scMpes’ plMy hugely influentiMl roles in the ecology of pelagic organisms, some of which never encou n ter benthic geography . For example, Yu et al. (2011) studied the correlation Netween the pH ‘lMn d scMpe’, or whMt they refer to Ms the “oceMn Mcidific a tion seMscMpe”, of neMrshore waters off California and the calcification of urchin larvae. Most fascinating of all, though, is the applic a- tion of landscape metrics which define pelagic distributions of biota as seascapes the m selves. Mitchell et al. (2008) described complex spatial arrangements of phytoplankton in the water column this way . These biological ‘ patches ’ influence e cological fun c tions, community dynamics, and biodiversity in much the same way as do ge o graphic landscapes and seascapes , and they are, in turn, influenced by physical param e- ters like turbulence . PhytoplMnkton pMtches don’t last long, only on the order of 10 0 to 1000 seconds, but non e theless they are distinctive enough to allow conceptual modeling of their distribution, which has implic a tions for determi n- ing grazing efficiency and taxonomic diversity of predatory species. It also emphasizes the concept of sc ale in the context of time in addition to space; these biolog i cal seascapes might not be obvious at large tim e scales, but become readily apparent when that scale is narrowed appropriately. This is probably the case with other dynamic mosaics, such as chemical seascapes. It should be noted, though, that no landscape (terrestrial or marine) is perfec t ly static ; appreciating the lifespan of mosaics is critical in recognizing spatial patterns which might be masked by assuming inappropr i- ate tim e scales. Coral reef connectivity and management From the plethora of studies concern ing m a rine ecology , we know that aquatic biota is indeed responsive to pelagic and benthic se a scapes ; by comparison, though, little has been done to assess these relationships in the way that lan d scape ecology has done for terrestrial systems (Boström et al. 2012). However, several studies have used these metrics to analyze aspects of coral reef eco - spatial relationships (Mumby 2006, Olds et al. 2012, Berkström et al. 2012, Moberg & Rönnbäck 2003) . T hese habitats provide a wonderful opportunity to assess correlations between flora, fauna, and the physical structure of the reef. Because of their incr edible biodiversity , it seems fundamental that we unde r stand how abiotic patterns influence sp ecies distribution throughout reef s , which could allow us to break down the ecological complexity of these systems and have enormous implications for the management of reefs worl d wide. Mumby (2006) attempted to accomplish some of these goals by correlatin g the availability of ma n grove nursery habitats with the health of adul t reef fish, and then translating these results into algorithms tha t inform management practices . The algorithms are fundame n tally landscape - ecology - derived metrics , and assess the spa tial distribution of Caribbean ma n groves that provide high - quality habitat for juvenile fish, the conne c- tivity between nursery sites and adult reef habitat, the relative i m portance of mangroves in providing nursery habitats for key reefs, and those ma n- grov es which are of highest priority for restor a- tion. These algorithms are all important in understan d ing the affect of mangrove - reef spatial relatio n ships on reef community structure and biological sustainability, and operate in much the same way as similar metrics (like connectivity) do in terre s trial systems. Most recently, Olds et al. (2012) looked sp e- cifically at the correlation between mangrove - reef connectiv i ty and reef complexity. They describe corMl reefs Ms “mosMics of seemingly disjointed [habita ts] that are fun c tionally connected by the movement Mnd dispersMl of orgMnisms”, heighte n- ing the ecological parallels that exist between terrestrial and marine systems, and thus justifying the application of traditional lan d scape metrics in aquatic environ ments. Using a combination of field surveys and satellite imagery, benthic habitat classifications (including coral reef s , mangrove s , seagrass bed s ) were identified, and five spatial pattern metrics were used to quantify connectivity between patches. The y specifically highlight the importanc e of scaling so that results are meanin g- ful and appropriate to the particular species of interest. These methods and concerns exactly mirror the approach of traditional lan d scape NRS 534 Term Paper BJC Fuller / Advances in seascape ecology: applying landscape metrics to marine systems 3 ( 5 ) Ecol Fragmented Landscapes / April 2013 © 2013 (REV 118 ) 20130429 ecolo gy, reinforcing the universality of basic ecological norms across all ecosystems. In broader terms, Berkström et al (2012) d e- scribe coral reefs as part of a more comprehensive ne t work of patches, including mangroves and seMgrMss Neds, which they cMll “the tropicMl seMscMpe”. In their ext ensive review of ecological connectivity in tropical seascapes, they find that the role of migrating fish in providing this connectivity is not well - understood through any particular study. However, through their asses s- ment of what little has been learned on the topic, it is clear that these fish probably perform a number of ecologically important functions and should be studied more heavily in the future. They also draw conclusions about the importance of understanding connectivity throughout the tropica l seascape in the context of reserve design and placement; while coral reefs are often the highest priority in dete r mining the location of marine protected areas (MPAs), interlinked patches like mangrove and seagrass beds are rarely included. By appreciat ing the role of connectivity between these patches in collectively maintaining them, MPAs might be expanded to include habitats which support reefs via these important biotic and abiotic pathways ; if the entire network is not protected, MPAs will have litt le chance of effectively maintaining high - priority patches. These metrics can also answer a number of i m portant non - MPA - related questions pertaining to human interaction with the tropical seascape. Moberg & Rönnbäck ( 2003 ) investigated coastal anthropogen ic pressures on the tropical seascape in order to address the limits of technological substitutes for ecosystem services (which they exemplify as artificial reefs, artificial seawalls, aquaculture in mangroves, etc.) and ways in which ecosystem restoration can not only rejuvenate these services but simultaneously result in a more resilient ecosystem. Some patch types, such as mangroves and seagrass beds, are more succes s- fu l ly restored than complex habitats like coral reefs. By understanding the interact ion between geographic heterogeneity (some of which we create ourselves) and the health of the biotic communities which are supported by it, we can begin to predict the impact various management techniques will have in a given ecosystem, which may subseque ntly help us determine the most appropriate patch types in which to apply those techniques. Patch connectivity, of course, is an integral part of the tropical seascape which must be considered for these techniques to be succes s- ful, especially when replaci ng ecosystem services with technological substitutes. The Moberg & Rönnbäck (2003) study emphasizes the i m- portance of recog nizing seascapes in developing manag e ment frameworks which foster eco - friendly technology and promote the resilience of both ecologi cal commun i ties and the societies that depend on them. Future considerations The application of landscape ecology to m a rine ecosystems seems obvious, nece s sary, and relatively seamless. For each terrestrial process assessed by landscape ecology, there i s likely an anal o gous marine process which can be assessed similarly. The future seems bright for this emerging field, which lies arguably at the cros s- roads of lan d scape and marine ecology. Metrics have already been applied to map ecosy s tem processe s like benthic production, turbidity, and denitrification, which advance our unde r standing of the functional value of coastal environments across large areas (Eyre & Maher 2011) . The study of sedimentary seascapes and the role of benthic invertebrates whi ch modify those mosaics (termed ‘ecosystem engineers’) is Mlso emerging, and is i m portant in extending seascape ecology on and into the seabed. New technology will allow us to study these systems at greater and greater depths. Mathematical mode l ing of su bterranean biological - geological intera c tions has already begun, and may result in new mode l ing methods that could eventually be applied to other seascapes and terrestr i al systems as well (Meadows et al. 2012). Other studies have investigated the influenc e of seascapes on pred a tion in coastal environments (Roliv & Schiel 2006) , allowing us to understand the dependency of these intera c- tions on geographic spatial patterns. This might cause us to revise previous models of predator - prey interactions to includ e metrics that consider patch composition, config u ration, and fractal dime n sion. Since many useful tools have already been developed through the study of landscape ecol o- NRS 534 Term Paper BJC Fuller / Advances in seascape ecology: applying landscape metrics to marine systems 4 ( 5 ) Ecol Fragmented Landscapes / April 2013 © 2013 (REV 118 ) 20130429 gy , and can be applied, without much modific a- tion, to marine environments, it is likely that seascape ecology will advance to an equal or near - equal state with landscape ecology relatively quickly. As is the case with most offshoots of well - established fields , tools developed specifically for seascape ecology will most likely help advance la ndscape ecology as well. The studies examined here point out a number of important consider a- tions that app ly to all eco - spatial analysis . T he potential of seascape ecology in complementing biological oceanography and marine ecology , as well as informing ecosystem - based management practi c es, seems timely and powerful, and is perhaps the missing link in solvi ng many of the marine ecological prob lems facing the s cie n tific , pol i cy , and management communities today. Berkström C, Gullström M, Lindborg R, Mwandya AW, Yahya SAS, Kautsky N, Nyström M. 2012. Exploring ‘knowns’ and ‘u n- knowns’ in tropical seascape connecti v ity with insights from East African coral reefs. Estuar Coast Shelf S 107:1 - 21  This is a very comprehensive r e view of literature on the co n ne c tiv i ty between coral reefs and supporting habitats like ma n groves and seagrass beds, with a focus on ecosy s tems in East Africa. They r e fer to the mosaic of these pa tches as “the trop i cal se a scape” and find that the co n nectivity between patches is rel a tively poorly unde r stoo d, especially with regard to the role of migratory fish as bi o logical linkers . The actual a r ticle itself is relatively brief, but paper includes extremely comprehensive tables su m marizing the documentation of fish species around Zanz i bar Island off Tanz a nia, and stu d ies on fish conne c tivity between various habitats. They emphasize that it is i m portant to approach environmental management from the perspective of seascapes, as o p posed to habitats, since this approach takes into account the connectivity and relative i m portance of each patch within the ecosy s tem mosaic. There is a lot of info r mation in this article, but identific a tion of main points w as not difficult. It seems that much of the detailed data would be useful in subsequent papers focu s ing specifically on the ecology and biology of fishes in the Zanzibar region, but not in drawing general conclusions about connectivity and se a scapes in a more global sense. Boström C, Pittman SJ, Simenstad C, Kneib RT. 2011. Seascape ecology of coastal benthic habitats: advances, gaps, and cha l- lenges. Mar Ecol Prog Ser 427:191 - 217  This article appeared in a Marine Ecology Progress Series theme section focusing on seascape ecology, a special ed i tion edited in part by the authors of Pittman et al. (2011). It is a highly useful review article that highlights both ar e as of progress and of need in the field, and evaluates the response of biota to fra g me n- tat ion in various marine ha b itats. Along with Pittman et al. (2011) and Wedding et al. (2011), this article provides some wonderful background to the emerging field of seascape ecol o gy and was critical in cross - referencing several key pieces of information. The variety of topics covered (e.g. the i m portance of scale; effects of patch size, edge, and fragmentation; g e o morphology in salt marshes; connectivity in coral reefs and mangroves) make it a lengthy paper, but numerous tables, graphs, and maps help ill ustrate the main points more quickly. However, a comprehe n- sive read is a must if the actual methods and appl i cation of landscape metrics used to generate the data are to be understood. Eyre BD, Maher D. 2011. Mapping ecosystem processes and function acro ss shallow seascapes. Cont Shelf Res 31:S162 - S172  This paper exemplified the power of u s ing landscape me t rics to map coastal ecosystem functions over various scales in various hab i tats. This information can then be used to ident i fy conse r v a- tion ‘hotsp ots’ and determine a r eas of high and low value to the overall health of the ec o system. This particular study f o cused on mapping lagoons and river estuaries in Australia . In add i tion to maps, the data can be summarized using innov a tive diagrams, which pro vide a visual way to quic k ly co m pare the value of functions across different habitat class i fications. The paper is not a difficult read, and any text which might need clarification can usually be understood by studying the figures. Meadows PS, Meadows A, Murray JMH. 2012. Biological modifiers of marine benthic seascapes: their role as ec o sy s tem engineers. Geomorphology 157 - 158:31 - 48  This article reviews research on the role of marine benthic o r ga n isms in modifying the seabed seascape. The study i n tr o du c- es the idea of advanced mathemat i cal modeling of this system, a concept which could be applied to other se a scape/landscape systems. It also discusses the i m portance of looking at the fossil record in determi n ing the intera c tion of biological and geolog ical pr o cesses that contributed to the formation of pr e sent seabed seascapes and sediment compos i tion. Key points in the paper are summ a rized in flow charts and diagrams, which are i n cre d ibly useful in generalizing concl u sions drawn from analysis conducte d on the species level. Their review is long and in - depth, and given the density of the paper their conclusions did not seem as compr e- he n sive as it could have been. Mitchell JG, Yamazaki H, Seuront L, Wolk F, Li H. 2008. Phytoplan k- ton patch patterns: Se ascape anatomy in a turb u lent ocean. J Marine Syst 69:247 - 253  This is a fascinating study which applied seascape ecology metrics to describe pa t terns of phyt o plankton patches . These patches arise partly in response to turbulence and eddy cu r rents, and form distinctive asymme t ric patches with regular distribution. The study was most inte r esting for its recognition of biological distributions as seascapes in and of themselves, which seems to be a relatively new co n cept. It also emphasizes the importanc e of apprecia t ing tim e scales when applying lan d scape metrics and re c ogni z ing se a scapes; otherwise certain mosaics might not be reco g nized as seascapes if inappr o priate timescales are used. The study used in situ fluorescence to identify plankton patches a nd correlated these with measures of physical oceanographic parameters such as salinity and temper a ture. Some graphs were difficult to comprehen d; ho w ever the conceptual 2D di s tributions were very fasc i nating. Moberg F, Rönnbäck P. 2003. Ecosystem servic es of the tropical seascape: interactions, substitutions and rest o ration. Ocean Coast Manage 46:27 - 46  This is a rather elegant art i cle which assesses the tropical se a scape in a t tempt to answer two fund a mental management que s tions: to what extent can te c h nological substitutes for NRS 534 Term Paper BJC Fuller / Advances in seascape ecology: applying landscape metrics to marine systems 5 ( 5 ) Ecol Fragmented Landscapes / April 2013 © 2013 (REV 118 ) 20130429 ecosystem services be effective, and how can ecosystem rest o r a- tion result in both the return of those services and the resil i ence of the system to future di s turbances. It is an important article for understanding the potential of se a scape ecology in a manag e- ment context, and does a good job of providing bac k ground information about each patch type as well as examples of ma n- ag e ment projects that have been successful because of their integration within the tropical se a scape patch mosaic. Mumby, PJ. 2006. Connectivity of reef fish between mangroves and coral reefs: Algorithms for the design of m a rine reserves at seascape scales. Biol Conserv 128:215 - 222  This study synth e sized data on mangrove nurseries and the health of adult r eef fish to develop four algorithms which i n form ma n ag e ment efforts in ma n grove habitats. The study was fairly compr e hensive, using landscape metrics to assess conne c tivity and patch i m portance throughout the Carribean. Info r mation was well - organized and summarized in both tabular and grap h ic formats, which made it easier to identify the ove r all results and implic a tions of the study. This article was crucial for hig h lighting the application of seascape ecology in directing ma n agement practi c es , since thi s a r ea of seascape ecology is as of yet underd e- veloped. Olds AD, Connolly RM, Pitt KA, Maxwell PS. 2012. Prim a cy of seascape connectivity effects in structuring coral reef fish a s semblages. Mar Ecol Prog Ser 426:191 - 203  This study f o cused specifically on using metrics to assess the connectivity of ma n groves and coral reefs, and the role of such conne c tivity in maintaining healthy adult reef fish assemblages. This was an important article in provi d ing an in - depth look at how these metrics can be applie d to marine connectivity, and built upon Mumby (2006). Reading was not terribly dense, but r e quired some special knowledge of reef fish assemblages and coral reef/mangrove ecology in order to fully appreciate the r e sults. Pittman SJ, Kneib RT, Simenstad CA. 2011. Practicing coastal seascape ecology. Mar Ecol Prog Ser 427: 187 - 190  This is a highly useful review article that appeared as the lead paper in a Marine Ecology Progress Series theme section focu s ing on se a scape ecology. The a u thors were also the ed i tors of the section, along with Ivan Nagelkerken, professor at The University of Adelaide in Austra l ia. It discusses the eme r gence of seascape ecology as a subset of marine ecology, hig h lights various e x a m ples of marine spatial patterns, and points to some i m portant dire c- tions for the future study of seascape ecol o gy. This was a perfect article to provide some necessary bac k ground about the develo p- ment of seascape ecology and the generally application of landscape metrics to m a rine sy s tems. Likewi se, it seemed to serve as an introdu c tion to the remainder of the theme section, which made it easier to relate subsequent articles to each other throughout the research process. Rilov G, Schiel DR. 2006. Seascape - dependent subtital - intertidal trophic lin kages. Ecol 87:731 - 744  This paper looked at settl e ment, predation, and trophic linka g es b e tween fish, crab, and mussel species in coastal env i- ro n ments around New Zealand. The goal was to understand the relationship between these predator - prey intera c t ions and the seascape itself, with considerations for scale . It was prima r ily interesting for this reason, since the study of predator - prey interactions often acknowledge the i n fluence of geographic heterogeneity, but only in the co n text of accounting for errors in modeling. The applic a tion of seascape ecology in unde r standing predator - prey i n tera c tions could have huge implic a tions for revising mo d els and explaining and removing errors in the analysis. The paper is heavy on statistics, which makes unde r- stan d ing the extent of the significance of interactions difficult without a working knowledge of multivariate ANOVA. Trophic webs help illustrate these interactions in the co n text of seascapes when statistical specifics aren’t nece s sary for conve y ing over all co n clusions, which make the paper a bit more pala t able. Wedding LM, Lepczyk CA, Pittman SJ, Friedlander AM, Jorgensen S. 2011. Quantifying seascape structure: e x tending terre s trial spatial pattern metrics to the marine realm . Mar Ecol Prog Ser 427:21 9 - 232  This is a very comprehensive r e view article that appeared in a Marine Ecology Progress Series theme section focusing on se a- scape ecology, which was edited in part by the authors of Pitmann et al. (2011). It gives a ge n eral background about the o rigins of seascape ecology, and covers a d vancements in some important topics including 2D and 3D seascape applic a tions, the influence of scale, analytical techniques, and general pro b lems encountered. Di a grammat i cal representations of analyt i cal problems and factors that influence the accuracy of se a scape metrics help illustrate the main points made in what is otherwise a straight - forward but fairly dense read. Along with Pittman et al. (2011) and Boström et al. (2011), this article provides a nice overvi ew of the a d vancements in seascape ecology and gives suggestions for future directions. Cross - referencing between these three art i cles proved highly useful. Yu PC, Matson PG, Martz TR, Hofmann GE. 2011. The ocean acidification seascape and its relationsh ip to the performance of calcifying marine invertebrates: Labor a tory experiments on the development of urchin larvae framed by environmentally - relevant pCO2/pH. J Exp Mar Biol Ecol 400:288 - 295  This study looks at the rel a tionship between pH ‘landscapes ’, or what they refer to as the “ocean acidification seascape”, and the ability of u r chin larvae to calcify their exoskeleton. This paper was fasc i na t ing for its treatment of seascapes in a che m ical, as opposed to geographic, context, which was especially enlighte n- ing. This invites a much broader perspective on the application of the term seascape , and perhaps ushers in a new vein of seascape ecology that can be applied to wholly pelagic organisms that never encounter any sort of physical landscape .