Percent Cover Of Algae Research Articles

DEFENDED TERRITORIES OF AN AGGRESSIVE DAMSELFISH, POMACENTRUS TRILINEATUS, IN THE NORTHERN RED SEA, HURGHADA, EGYPT

The territorial behavior of the pomacentrid damselfish Pomacentrus trilineatus was studied on three reefs in the northern Red Sea, Hurghada, Egypt in order to investigate difference between defended and undefended areas. Seven families of reef fishes (Pomacentridae, Chaetodontidae, Acanthuridae, Labridae, Scaridae, Holocentridae and Siganidae) were dominant among the 21 recorded families at study sites. The territories of P. trilineatus were very small in area, ranging from 0.7 to 0.9 m2. Remarkable variation was observed for substrate composition between both inside (defended) and outside (undefended) P. trilineatus territories. Eight genera of hard corals were recorded inside P. trilineatus territory of them four genera were dominant and widespread outside the territory. Two soft coral genera were recorded inside and outside territory of P. trilineatus. Fleshy algae were dominant inside P. trilineatus territory. Three groups of associated fauna (Molluscs, Echinoderms and sponges) were recorded inside territory of P. trilineatus while two groups (Molluscs and Echinoderms) were recorded outside territory. Dead components of substrate showed more dominance outside the territory than inside. The percentage cover of algae had the highest values inside territory especially fleshy algae while that of hard corals had the highest values outside territory. Nine species belonging to four families were resident inside P. trilineatus territory. Of the 60 species recorded, 42 species were intruders. Siganids, the fish P. trilineatus(which is not the territory holder), Scarus ghobban and the juvenile fish Chlorurus sordidus had the lowest trespass times recorded. P. trilineatus showed high number of agonistic acts against conspecifics, Siganus luridus, S. rivulatus and Rhinicanthus assai with strong level intensity (A). P. trilineatus did not show any agonistic acts against resident species. The highest values of agonism elicited were recorded against nonspecific, S. luridus, S. rivulatus, R. assai, C. sordidus (juv.) and S. ghobban. The fish existed in high numbers at study sites and found to cultivate its territory with high density of macro-algae and the algae were observed growing at faster rates inside the territories of the fish than outside. The fish found to defend aggressively herbivorous fishes and excluded them from its territory especially browser fishes. Such behavior is considered to have detrimental effects on benthic structure through allowing fleshy macro-algae to grow faster and out-compete coral recruitments for space.

Distribution and functional traits of polychaetes in a CO2 vent system: winners and losers among closely related species

This authors' personal copy may not be publicly or systematically copied or distributed, or posted on the Open Web, except with written permission of the copyright holder(s). It may be distributed to interested individuals on request. MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Vol. 550: 121–134, 2016 doi: 10.3354/meps11727 Published May 25 Distribution and functional traits of polychaetes in a CO 2 vent system: winners and losers among closely related species M. C. Gambi 1 , L. Musco 2, 6, *, A. Giangrande 3 , F. Badalamenti 2 , F. Micheli 4 , K. J. Kroeker 5 Stazione Zoologica Anton Dohrn - Integrative Marine Ecology, Villa Dohrn-Benthic Ecology Center, 80077 Ischia, Napoli, Italy Laboratory of Marine Ecology - IAMC - CNR, 91014 Castellammare del Golfo, Italy University of Salento, DiSTeBA, 73100 Lecce, Italy Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA University of California at Santa Cruz, Santa Cruz, CA 95064, USA Present address: Stazione Zoologica Anton Dohrn, 80121 Napoli, Italy ABSTRACT: We report on fine taxonomic and functional analyses of polychaetes associated with rocky reefs along a gradient of ocean acidification (OA) at the volcanic CO 2 vent system off the Castello Aragonese (Ischia Island, Italy). Percent cover of algae and sessile invertebrates (a deter- minant of polychaete distribution) was classified into functional groups to disentangle the direct effects of low pH on polychaete abundance from the indirect effects of pH on habitat and other species associations. A total of 6459 polychaete specimens belonging to 83 taxa were collected. Polychaete species richness and abundance dramatically dropped under the extreme low pH con- ditions due to the disappearance of both calcifying and non-calcifying species. Differences in dis- tribution patterns indicate that the decreasing pH modified the structure and biological traits of polychaete assemblages independent of changes in habitat. A detailed taxonomic analysis high- lighted species-specific responses to OA, with closely related species having opposing responses to decreasing pH. This resulted in an increase in the abundance of filter feeders and herbivores with decreasing pH, while sessile polychaetes disappeared in the extreme low pH zones, and were replaced by discretely motile forms. Reproductive traits of the polychaete assemblages changed as well, with brooding species dominating the most acidified zones. The few taxa that were abundant in extreme low pH conditions showed high tolerance to OA (e.g. Amphiglena mediterranea, Syllis prolifera, Platynereis cf. dumerilii, Parafabricia mazzellae, Brifacia aragonen- sis), and are promising models for further studies on the responses of benthic organisms to the effects of reduced pH. KEY WORDS: Annelida · Algal cover · Ocean acidification · Hard bottoms · pH gradient · Covariation · Mediterranean Sea · Functional trait analysis Resale or republication not permitted without written consent of the publisher Increased anthropogenic CO 2 emissions are pre- dicted to be among the major drivers of global change in the coming century in both terrestrial and marine ecosystems (Gattuso & Buddemeier 2000, IPCC 2014). Large among-species variation in bio- logical responses to CO 2 -induced ocean acidification (OA) is evident in the literature, but it is biased towards calcifying organisms (Ries et al. 2009, Kroeker et al. 2010, 2013a), with most available data derived from laboratory or mesocosm studies (Fabry et al. 2008, Feely et al. 2009, Kroeker et al. 2010, 2013a). However, recent studies performed in natu- *Corresponding author: luigi.musco@szn.it © Inter-Research 2016 · www.int-res.com INTRODUCTION

Spatial and depth-associated distribution patterns of shallow gorgonians in the Algarve coast (Portugal, NE Atlantic)

The ecological role of gorgonians for marine rocky bottoms is worldwide recognized, but the information on the distribution patterns of NE Atlantic temperate species is insufficient, considering current global, regional and local threats. To overcome the lack of information on the spatial distribution patterns of gorgonians in south Portugal, in 2009/2010, the occurrence and abundance of gorgonian species in rocky bottoms were quantified over more than 25 km of coast (37.1°N/8.6°W) down to 30 m depth. Eunicella labiata, Eunicella gazella, Eunicella verrucosa and Leptogorgia sarmentosa were abundant and frequent in the studied area, while Leptogorgia lusitanica was less abundant. All species evidenced a similar depth pattern, that is abundance significantly increased with depth below 15 m. At shallower waters (up to 15 m), the distribution of gorgonians may be constrained by abiotic factors and competition with algae. Indeed, the abundance of gorgonians was negatively correlated with the percentage cover of algae along the depth gradient, but gorgonians and sponges coexist. Competition among gorgonian species also seems to be low in this area because of the similarity in the abundance pattern observed for the most abundant species and also their high association. In NE Atlantic shallow temperate rocky bottoms, the distribution of gorgonians seems to be influenced by environmental factors and biological interactions, namely competition (algae) and coexistence (sponges and other gorgonians).

Algal cover in mangroves affects distribution and predation rates by carnivorous fishes

Distribution and survival of fish are influenced by benthic habitat and complexity. While many studies have investigated the effects of algal cover on fishes in reef habitats, comparatively less is known regarding this relationship in mangrove habitats. Possible links between substrate macro-algal cover and fish distribution were studied in a Caribbean mangrove lagoon via visual surveys and algal removal experiments. In addition, the effects of algae on relative predation were tested by calculating survival of tethered brachyuran prey, whose predators are known to include larger lutjanid (snapper) juveniles. Comparisons of algae and fish distributions show that percent cover of algae and juvenile lutjanid, Lutjanus griseus (gray snapper) abundances were significantly negatively correlated. Results from the algae removal experiment showed that algae had a negative effect on abundance of carnivorous fishes in two (out of three) locations in the lagoon. In addition, tethered prey had significantly higher proportional survival in plots with algae-present relative to plots with algae-absent. We present here experimental evidence that increased algal growth in mangroves may reduce predator encounter rates by prey. These observations are important, as the presence of carnivorous fishes is a key factor for the maintenance of high diversity in mangrove and on neighboring coral reefs. Furthermore, findings from this study imply that algal cover must be considered when protecting mangrove habitat.

Dynamics of fish assemblages on a continuous rocky reef and adjacent unconsolidated habitats at Fernando de Noronha Archipelago, tropical western Atlantic

In recent years, many studies investigated how density-dependent factors, such as shortages in microhabitat and food availability influence the structure of reef fish assemblages. Most of what is currently known, however, comes from comparisons of isolated patch reefs and from correlations between fish abundance and one or few microhabitat variables. In addition, most studies were done in the Caribbean and Indo-Pacific regions, whereas the South Atlantic region has been, to date, understudied. The present study evaluated spatial and temporal variations in reef fish abundance and species richness in a continuous rocky reef and adjacent unconsolidated habitats in a Southwestern Atlantic reef, using underwater techniques to assess both fish numbers and microhabitat variables (depth, rugosity, number of crevices and percent cover of live benthic organisms, bare rock, sand, and limestone). Higher species richness was observed at consolidated substratum stations on both sampling periods (May and October), but fish abundance did not show a significant spatial variation. Topographical complexity and percent cover of algae (except coralline algae) were amongst the most important determinants of species richness, and correlations between fish size and refuge crevice size were observed. The non-random patterns of spatial variation in species richness, and to a lesser extent, fish abundance, were related to differences in substratum characteristics and the inherent characteristics of fishes (i.e. habitat preferences) and not to geographical barriers restraining fish movement. This study highlights the importance of concomitantly assessing several microhabitat variables to determine their relative influence in reef fish assemblages.

Surf zone physical and morphological regime as determinants of temporal and spatial variation in larval recruitment

Larvae of intertidal species develop in the coastal ocean, and the last body of water they must cross while migrating back to shore is the surf zone. We hypothesized that the surf zone is a semipermeable barrier to this shoreward migration and that differences in water exchange across the surf zone result in temporal and spatial variation in larval delivery to the shore. We tested the hypotheses that larval delivery 1) should increase with larger waves and 2) should be higher on more dissipative beaches than on more reflective beaches. We found a significant positive correlation between the daily averaged ratio of wave height to wave period ( H/ T) and daily cyprid settlement at Dike Rock, California and Bastendorff Beach, Oregon, USA. We tested the second hypothesis by comparing populations of barnacles, limpets, and benthic algae on rocks on four more dissipative and six more reflective sandy beaches in northern California and southern Oregon. Newly recruited barnacles and limpets were significantly more abundant at more dissipative than reflective beaches, and the higher abundance was most likely due to differences in settlement rather than post-settlement mortality. The density and percent cover of barnacles and the density of limpets were significantly higher at more dissipative beaches. In contrast, the density and percent cover of algae were significantly higher at more reflective beaches. The results are consistent with the hypothesis that the surf zone is a semipermeable barrier to the shoreward migration of larvae and that differences in water exchange across the surf zone as function of the beach hydrodynamics result in temporal and spatial variation in larval delivery to the shore.

The invasion of the intertidal canopy-forming alga Fucus serratus L. to southwestern Iceland: Possible community effects

The intertidal serrated wrack, Fucus serratus L. (Fucales: Phaeophyceae), has become an abundant canopy-forming alga along a ca. 100 km stretch of shore in southwestern Iceland in the last century. Its distribution has not changed noticeably since a survey in 1975/1976. Many experimental studies have shown that canopy-forming algae can have profound effects on the community structure. Although such experiments involving F. serratus are few it was decided to test predictions from these experiments on a geographical scale by comparing community compositions within the area where F. serratus is a dominant algae (since at least 1975/1976) with an adjacent area of similar size where F. serratus is absent (with a single exception without consequences). The work is based on measurements on some 372 stations in the F. serratus area, termed region A, and 227 stations from the F. serratus-free area, termed region B. Percentage cover of algae and sessile invertebrates was estimated on 2 m 2 on each station and animals collected from 800 cm 2 from each station. The vertical distribution of F. serratus was most similar to that of Fucus distichus and the two species often grew intermingled on the lower part of the shore. F. serratus appeared to have reduced the cover of F. distichus in the lowermost part of the shore, while having little or no effect on other canopy-forming species. The low abundance of Semibalanus balanoides in the F. serratus area (region A) is in line with experiments showing detrimental effect on this barnacle by whiplash of F. serratus. In general algal grazers were more abundant in region A, consistent with the greater attractiveness of F. serratus than other canopy-forming species to grazers, although this may be partly explained by the abundance of understorey algae in region A.

Temporal changes in community structure of tide pools following the “Erika” oil spill

The impact of the Erika oil spill on the tidal rock pool community, and particularly on two species of sea urchin (Paracentrotus lividus and Psammechinus miliaris), was investigated over a 3-year period, at Piriac-sur- Mer (Department of Loire-Atlantique, France, 47 ◦ 21.6 � N; 2 ◦ 31.7 � W). A dramatic increase in the abundance of two macroalgae Ulva sp. and Grateloupia doryphora occurred following a 100% mortality of sea urchins observed three weeks after the oil spill. The density of sea urchins and of other main herbivores, the periwinkle Littorina littorea and the trochid mollusks Gibbula umbilicalis and Gibbula pennantii, were monitored between January 2000 and March 2003. There was significant inverse relationship between the overall density of herbivores (sea urchins, periwinkles and trochid mollusks) and the percent cover of algae in the tidal pools. The first urchins in the tidal pools were observed two years after the oil spill and it took three years to reach sea urchin densities comparable to the reference value of 63 ind.m −2 obtained before the oil spill.

Variability at different spatial scales of a coralligenous assemblage at Giannutri Island (Tuscan Archipelago, northwest Mediterranean)

This study was carried out on the rocky cliffs of Giannutri Island (Tyrrhenian Sea, Italy) to test the hypothesis that coralligenous assemblages are consistent within the bathymetric range considered (25–35 m depth) over three different spatial scales (1000 m, 100 m and 10 m). A multi-factorial sampling design was used to assess patterns of vertical distribution in the studied area. Data on the percent cover of algae and invertebrates were collected at three depths (25, 30 and 35 m) using a photographic method, and percentage cover was obtained using a visual method. Analysis of the results using ANOVA indicated that the distribution and abundance of algae and some invertebrates of the sublittoral assemblages are clearly heterogeneous. Algae, sponges and bryozoans showed significant variability in distribution and abundance at different depths, but this variability was not consistent amongst transects. Ascidians did not show any variability, while the abundance of anthozoans differed significantly amongst transects. We concluded that heterogeneity in the distribution and abundance of the taxa analysed is related to the smallest spatial scale investigated (10’s of m). Some of the possible causes of the observed variability are discussed.

Interactions between corals and algae on a temperate zone rocky reef: mediation by sea urchins

Interactions among sea urchins, algae, and a scleractinian coral were examined in a 10-year study off Anacapa Island, California. Abundances of the solitary cup coral Balanophyllia elegans Verrill and percent cover of algae were inversely correlated. Corals could be killed due to overgrowth by kelp holdfasts, ephemeral filamentous algae, or encrusting coralline algae. Overgrowth by filamentous and coralline algae was enhanced by chronic brushing by larger algal species which caused coral polyps to retract. Short- and long-term observations and manipulative experiments demonstrated that significantly more coral polyps were retracted and coral mortality was increased within the brushing zone of natural and artificial algae than in control areas without algae. Additionally, the extent of polyp retraction varied with algal species and degree of water motion. The adverse effects of algae on corals can be mediated by urchin grazing. High densities of urchins remove algae, thereby reducing coral mortality due to algal overgrowth and allowing corals to increase in abundance.

The Role of Grazers in the Zonation of Intertidal Macroalgae of the Chilean Coast

The role of herbivores in maintaining the pattern of zonation of macroalgae in the mid-intertidal community of semi-exposed shores was studied during 8 months (January to September 1979). Herbivores were totally removed every 15 days from a semi-exposed intertidal rocky wall, while another wall served as a control. Percent cover of algae was measured at two month intervals. Herbivore removal resulted in a disruption of the pattern of zonation. Iridaea boryana and Gymnogongrus furcellatus expanded the width of their belts into the zone initially occupied only by Ulva rigida and Lithophyllum spp. We conclude that herbivory is the basic mechanism which maintains the limits between the zones of these macroalgae in southern Chile.