Paper: “Recreational diving and its effects on the macroalgal communities of the unintentional artificial reef Zenobia shipwreck (Cyprus)”

paper-2-siciliano-et-al-2016

Siciliano Alfonso, Jimenez Carlos, Antonis Petrou

X

Abstract

The ecological role of shipwrecks as artificial reefs is well established and often is prime and exclusive destinations for diving tourism. But they are also extremely delicate and sensitive environments. For this reason, the impact of recreational diving on shipwrecks should be taken in consideration since diver’s experience can strongly affect their associated benthic communities. The aim of this study was to verify the impact of anthropogenic activities (scuba divers) on the macroalgal coverage, here considered as indicator of physical disturbance, on the modern shipwreck Zenobia, in Cyprus (east Mediterranean Sea). Divers behaviour was investigated in the wreck and the macroalgal coverage was determined (photo-quadrat method) in three areas differently exposed to physical contact of divers. Our results suggest that diving is having a significant negative effect on the macroalgae coverage of the shipwreck, especially in areas subject to high levels of use (e.g., meeting stations) when compared to control sites in the same wreck. Divers’ behaviour and popular dive routes at the wreck are factors associated to the observed decrease in macroalgae benthic cover. It is important that relevant stakeholders utilizing the Zenobia wreck agree on basic management planning in order to protect and enhance the wreck’s biodiversity. In addition, this study provides for the first time evidence of ecological deterioration of one of the most emblematic shipwreck of the Mediterranean Sea.

Paper: “A sixth-level habitat cascade increases biodiversity in an intertidal estuary”

paper-1-thomsen-et-al-2016

Mads S. Thomsen, Thomas Hildebrand, Paul M. South, Travis Foster, Alfonso Siciliano, Eliza Oldach, David R. Schiel

X

Abstract

Many studies have documented habitat cascades where two co-occurring habitat-forming species control biodiversity. However, more than two habitat-formers could theoretically co-occur. We here documented a sixth-level habitat cascade from the Avon-Heathcote Estuary, New Zealand, by correlating counts of attached inhabitants to the size and accumulated biomass of their biogenic hosts. These data revealed predictable sequences of habitat-formation (= attachment space). First, the bivalve Austrovenus provided habitat for green seaweeds (Ulva) that provided habitat for trochid snails in a typical estuarine habitat cascade. However, the trochids also provided habitat for the non-native bryozoan Conopeum that provided habitat for the red seaweed Gigartina that provided habitat for more trochids, thereby resetting the sequence of the habitat cascade, theoretically in perpetuity. Austrovenus is here the basal habitat-former that controls this “long” cascade. The strength of facilitation increased with seaweed frond size, accumulated seaweed biomass, accumulated shell biomass but less with shell size. We also found that Ulva attached to all habitat-formers, trochids attached to Ulva and Gigartina, and Conopeum and Gigartina predominately attached to trochids. These “affinities” for different habitat-forming species probably reflect species-specific traits of juveniles and adults. Finally, manipulative experiments confirmed that the amount of seaweed and trochids was important and consistent regulators of the habitat cascade in different estuarine environments. We also interpreted this cascade as a habitat-formation network that describes the likelihood of an inhabitant being found attached to a specific habitat-former. We conclude that the strength of the cascade increased with the amount of higher-order habitat-formers, with differences in form and function between higher and lower-order habitat-formers, and with the affinity of inhabitants for higher-order habitat-formers. We suggest that long habitat cascades are common where species traits allow for physical attachment to other species, such as in marine benthic systems and old forest.

Conference: “Effects of seaweeds, nutrients and sedimentation on seagrass and seagrass-associated fauna”

08-abc-conference-2016

Annual Biology Conference (ABC) 2016, University of Canterbury, New Zealand

X

Abstract

Seagrasses are marine plants that take up nutrients, stabilize sediments, increase habitat complexity and thereby also increase biodiversity of sedimentary coastal ecosystems. Seagrasses also facilitate seaweeds that can become entangled around seagrass leaves and stems. However, relatively little is known about interactions between entangled seaweeds and seagrass, their effects on seagrass-associated invertebrates and if their interactions are modified by abiotic conditions, like nutrient and sedimentation levels. We aimed to test the hypotheses that (i) seaweeds have negative effects on seagrass (competing for limited resources) but positive effect on invertebrate biodiversity (by increasing habitat-complexity), across seasons in the Avon-Heathcote estuary, (ii) that similar processes occur in other estuaries, and (iii) that the magnitude of effects increases with increasing levels of inorganic nutrients and sediments. To test the first two hypotheses, we collected cores from the Avon-Heathcote estuary and from six other estuaries. To test the third hypothesis, we manipulated nutrient and sedimentation levels in two field-experiments. Preliminary data analysis supports our hypotheses: seaweeds had negative impact on seagrass but positive effects on the abundance of many invertebrates. We also found that enhanced sediments, but not nutrients, had strong negative impact on seagrass with cascading negative impacts on the invertebrate community.

Conference: “Epiphytism as key driver of biodiversity in canopy-forming seaweeds-dominated systems”

06-itrs-2016

11th International Temperate Reefs Symposium (ITRS) 2016, University of Pisa, Italy

X

Abstract

It is well established that host species that are morphologically and genetically different can support different epibiotic species, and that these differences can support different invertebrate communities. However, no studies have tested the opposite hypothesis of whether morphologically similar congeneric hosts support similar epibiota and have similar cascading effects on invertebrate communities. This hypothesis was tested with mensurative and manipulative experiments using three conspecific, morphologically similar marine seaweed hosts: the canopy-forming fucoids Cystophora torulosa, C. scalaris, and C. retroflexa. In the mensurative experiment, hosts, epiphytes and associated invertebrate communities were sampled and enumerated from 4 tide-pools (>1 m apart), at 2 reefs (>1 km apart) and 4 sites (>100 km apart). In two follow-up manipulative experiments, defaunated hosts, epiphytes and epiphytes’ mimics were combined and transplanted to shared tide pools and the epifaunal recolonization was quantified. Both experiments suggest that epiphytism increases abundances and richness of invertebrates, across host species, epiphyte species, sites, regions, and experimental methods, demonstrating its key role in sustaining the epifaunal community. However, the experiments reject the initial hypothesis since congeneric and morphologically similar hosts appear to support a different epifauna and having different cascading effects.

Conference: “Cascading effects of epiphytism associated with co-occurring congeneric hosts”

03-nzes-conference-2015

New Zealand Ecological Society (NZES) 2015, University of Canterbury, New Zealand

X

Abstract

It is well established that host species that are morphologically and genetically different can support different epibiotic species, and that these differences can support different invertebrate communities. However, no studies have tested the opposite hypothesis of whether morphologically similar congeneric hosts support similar epibiota and have similar cascading effects on invertebrate communities. This hypothesis was tested with mensurative and manipulative experiments using three conspecific, morphologically similar marine seaweed hosts: the canopy-forming fucoids Cystophora torulosa, C. scalaris, and C. retroflexa. In the mensurative experiment, hosts, epiphytes and associated invertebrate communities were sampled and enumerated from 4 tide-pools (>1 m apart), at 2 reefs (>1 km apart) and 4 sites (>100 km apart). In two follow-up manipulative experiments, defaunated hosts, epiphytes and epiphytes’ mimics were combined and transplanted to shared tide pools and the epifaunal recolonization was quantified. Both experiments suggest that epiphytism increases abundances and richness of invertebrates, across host species, epiphyte species, sites, regions, and experimental methods, demonstrating its key role in sustaining the epifaunal community. However, the experiments reject the initial hypothesis since congeneric and morphologically similar hosts appear to support a different epifauna and having different cascading effects.