Impacts of alien ‘ecosystem engineers’ overwhelm interannual and seasonal shifts in rocky-shore community composition on Marcus Island, South Africa

The South African coastline has been invaded by numerous alien species. Rare pre-invasion (1980) and post-invasion datasets (2001 and 2012) exist for Marcus Island, a small land-tied island in Saldanha Bay, South Africa. These snapshot datasets of the island’s intertidal invertebrate community were complemented with monitoring across seasons, from 2014 to 2016. Invertebrate communities were compared among the summers of 1980, 2001, 2012, 2014, 2015 and 2016 to assess interannual differences, while invertebrates and algae were monitored quarter-annually to assess seasonal changes. In addition, the population dynamics of the alien mussel Mytilus galloprovincialis were monitored. Differences in invertebrate communities between consecutive summers were significant but much smaller than changes induced by the arrival of alien species. Invertebrate and seaweed communities differed among years and shore zones but not among seasons, whereas species diversity differed among years, seasons and shore zones, with zones having the strongest influence. The invasion by M. galloprovincialis, and ensuing spatial and temporal variability in its recruitment, emerged as the most important factor influencing community composition, overshadowing interannual and seasonal changes. This work highlights that the impacts of alien species can be distinguished from natural variability by combining long-term monitoring with surveys at finer temporal scales. This is an important step in extending our understanding of the impacts of marine alien species.

[1]  Stephen J. Hawkins,et al.  The role of kelp species as biogenic habitat formers in coastal marine ecosystems , 2017 .

[2]  S. Hawkins,et al.  The influence of mussel-modified habitat on Fucus serratus L. a rocky intertidal canopy-forming macroalga , 2016 .

[3]  T. Robinson,et al.  Lost in translation? Standardising the terminology used in marine invasion biology and updating South African alien species lists , 2016 .

[4]  J. Assis,et al.  Oceanographic Conditions Limit the Spread of a Marine Invader along Southern African Shores , 2015, PloS one.

[5]  T. Robinson,et al.  Changes in habitat complexity resulting from sequential invasions of a rocky shore: implications for community structure , 2015, Biological Invasions.

[6]  T. Noda,et al.  Early phase of the invasion of Balanus glandula along the coast of Eastern Hokkaido: changes in abundance, distribution, and recruitment , 2014, Biological Invasions.

[7]  C. Griffiths,et al.  Deja vu? A second mytilid mussel, Semimytilus algosus, invades South Africa's west coast , 2013 .

[8]  C. Johnson,et al.  The effects of an invasive habitat modifier on the biotic interactions between two native herbivorous species and benthic habitat in a subtidal rocky reef ecosystem , 2013, Biological Invasions.

[9]  M. Ortiz,et al.  Network properties and keystoneness assessment in different intertidal communities dominated by two ecosystem engineer species (SE Pacific coast): A comparative analysis , 2013 .

[10]  J. Creed,et al.  Change in tropical rocky shore communities due to an alien coral invasion , 2011 .

[11]  R. Scrosati,et al.  Variation in Community Structure across Vertical Intertidal Stress Gradients: How Does It Compare with Horizontal Variation at Different Scales? , 2011, PloS one.

[12]  N. J. Frost,et al.  Interactive effects of losing key grazers and ecosystem engineers vary with environmental context , 2011 .

[13]  T. Robinson,et al.  Competition and facilitation between the alien mussel Mytilus galloprovincialis and indigenous species: Moderation by wave action , 2010 .

[14]  G. M. Branch,et al.  Long-term monitoring of the arrival, expansion and effects of the alien mussel Mytilus galloprovincialis relative to wave action , 2008 .

[15]  C. Griffiths,et al.  Present distribution and abundance of the introduced barnacle Balanus glandula Darwin in South Africa , 2008 .

[16]  P. Hockey,et al.  Changes in South African rocky intertidal invertebrate community structure associated with the invasion of the mussel Mytilus galloprovincialis , 2007 .

[17]  C. McQuaid,et al.  Re-colonisation rate differs between co-existing indigenous and invasive intertidal mussels following major disturbance , 2006 .

[18]  Sergej Olenin,et al.  Are aliens threatening European aquatic coastal ecosystems? , 2006, Helgoland Marine Research.

[19]  Nessa E. O'Connor,et al.  Effects of epibiotic algae on the survival, biomass and recruitment of mussels, Mytilus L. (Bivalvia: Mollusca) , 2006 .

[20]  T. Robinson,et al.  Marine alien species of South Africa — status and impacts , 2005 .

[21]  G. M. Branch,et al.  Can we predict the effects of alien species? A case-history of the invasion of South Africa by Mytilus galloprovincialis (Lamarck) , 2004 .

[22]  C. Steffani,et al.  Spatial Comparisons of Populations of an Indigenous Limpet Scutellastra Argenvillei and an Alien Mussel Mytilus Galloprovincialis Along a Gradient of Wave Energy , 2003 .

[23]  R. Kado.  Invasion of Japanese shores by the NE Pacific barnacle Balanus glandula and its ecological and biogeographical impact , 2003 .

[24]  B. Kelaher,et al.  Changes in habitat complexity negatively affect diverse gastropod assemblages in coralline algal turf , 2003, Oecologia.

[25]  Richard C. Thompson,et al.  Rocky intertidal communities: past environmental changes, present status and predictions for the next 25 years , 2002, Environmental Conservation.

[26]  S. Hawkins,et al.  Intertidal Rocky Shore Communities of the Continental Portuguese Coast: Analysis of Distribution Patterns , 2002 .

[27]  G. Quinn,et al.  Experimental Design and Data Analysis for Biologists , 2002 .

[28]  A. Dye.  Dynamics of Rocky Intertidal Communities: Analyses of Long Time Series from South African Shores , 1998 .

[29]  R. Bustamante,et al.  The influences of physical factors on the distribution and zonation patterns of South African rocky-shore communities , 1997 .

[30]  B. J. Wilson,et al.  Biologically generated habitat provision and diversity of rocky shore organisms at a hierarchy of spatial scales , 1996 .

[31]  R. Bustamante,et al.  Large scale patterns and trophic structure of southern African rocky shores: the roles of geographic variation and wave exposure , 1996 .

[32]  J. Lawton,et al.  Organisms as ecosystem engineers , 1994 .

[33]  S. Hawkins.  Interactions of Patella and macroalgae with settling Semibalanus balanoides (L.) , 1983 .

[34]  G. Branch.  Interspecific Competition Experienced by South African Patella Species , 1976 .

[35]  Joseph H. Connell,et al.  Community Interactions on Marine Rocky Intertidal Shores , 1972 .

[36]  E. Schwindt,et al.  Introduced and native species on rocky shore macroalgal assemblages: zonation patterns, composition and diversity. , 2014 .

[37]  F. Arenas,et al.  Biological Invasions: Insights from Marine Benthic Communities , 2009 .

[38]  G. Quinn,et al.  Experimental Design and Data Analysis for Biologists: Comparing groups or treatments – analysis of variance , 2002 .

[39]  M. Tokeshi.  Polychaete abundance and dispersion patterns in mussel beds: a non- trivial "infaunal' assemblage on a Pacific South American rocky shore , 1995 .

[40]  L. Romero,et al.  Filling a gap:dynamics of space occupancy on a mussel-dominated subtropical rocky shore , 1995 .

[41]  P. Hockey,et al.  The invasive biology of the musselmytilus galloprovincialison the southern african coast , 1992 .

[42]  K. Miller,et al.  The role of spatial and size refuges in the interaction between juvenile barnacles and grazing limpets , 1989 .

[43]  S. Hawkins,et al.  Grazing of intertidal algae by marine invertebrates , 1983 .