Giuliano Buzá Jacobucci

Temporal variation of amphipod assemblages associated with Sargassum filipendula (Phaeophyta) and its epiphytes in a subtropical shore

The phytal assemblages change in response to variation in biological and environmental conditions. In the present study, we evaluated the temporal variation of amphipod assemblages associated with a Sargassum filipendula bed in a subtropical shore, in relation to variation of the host alga, its epiphytes and local environmental conditions. Samples of S. filipendula with associated amphipods, water temperature, water movement and suspended solids were obtained monthly from June 2000 to May 2001. We recorded 24 species of amphipods associated with S. filipendula. Species richness varied throughout the year, with maximum values in October 2000 and minimum in April 2001. Total amphipod density gradually increased during the sampling period, with the highest value in March 2001. Amphipod diversity and evenness were both positively influenced by epiphyte load and negatively by temperature, with higher values during summer months. Total density and tube-builder density were also positively influenced by temperature, whereas nestler density was influenced by epiphyte load. Individual amphipod species showed significant density fluctuations over the year. The canonical correspondence analysis performed explained 88.2% of the variation, with a strong correlation of water movement, temperature and suspended solids with the first axis, and a strong effect of epiphyte load on both the first and the second axes. The temporal structural variation of the studied algal bed strongly influenced amphipod diversity and assemblage composition, possibly through direct and indirect effects.

Levantamento de Mollusca, Crustacea e Echinodermata associados a Sargassum spp. na Ilha da Queimada Pequena, Estacao Ecologica dos Tupiniquins, litoral sul do Estado de São Paulo, Brasil

This work represents the first effort to assess the phytal macrofauna of Queimada Pequena island and was focused in mollusks, crustaceans and echinoderms associated to Sargassum spp. Sampling of the macrofauna was performed by random collections of 6 Sargassum fronds 6 m deep using SCUBA. The fronds were sealed underwater in individual 200 mm mesh bags and detached from the rocky shore. The samples were preserved in recipients in 10% formalin and carried to the laboratory to remove and identify the associated fauna. Forty one taxa were registered, with dominance of peracarid crustaceans. Mollusk composition is different from that of northern Sao Paulo coast. From the sixteen mollusk species recorded, only the gastropod genera Anachis and Odostomia and the bivalves Musculus and Modiolus were recorded in the Sargassum macrofauna at both coastal regions of Sao Paulo state, although the genus Fissurela had already been recorded at Santos region associated with the alga Amphiroa fragilissima. The occurrence of the exotic bivalve Isognomon bicolor was also confirmed. Our data suggest differences in the composition of molluskan fauna between southern and northern coasts of the state. Extensive investigations are necessary to confirm these results and to support management strategies in this conservation unit.

Dieta e comportamento alimentar de Malacoctenus delalandii (Perciformes: Labrisomidae)

article+bn01808032008 Abstract: This work analyzed the diet composition and the feeding behavior of Malacoctenus delalandii, a carnivorous species, with diurnal habit, that lives in holes and crevices of rock areas in tropical waters. For diet evaluation, 31 individuals were collected during diving using hand nets, in the Fortaleza beach, Ubatuba. The feeding offer was analyzed comparing the stomach contents of the collected individuals with ten samples of the Amphiroa beauvoisii calcareous algal phytal, the species foraging site. To describe the feeding behavior of M. delalandii 44 observation sections were performed using ad libitum and focal animal methods. The food items considered constant were crustaceans belonging to the order Isopoda (75.8%) and the suborder Gammaridea (86.2%), confirming the species carnivorous feeding habit. There was a significant difference (G = 278.89, df = 70, p < 0.01) between the availability of items in the substrate and the occurrence in the stomachs. A total of 410 minutes (6.8 hours) of direct underwater observations were performed, and we concluded that the individuals use the grubber excavation while moving feeding strategy. The species presented a foraging rate of 0.74 ± 0.164 bites per minutes (average ± standard deviation), evidencing low feeding activity and cryptobenthic habit.

Seasonal variation of epiphytic hydroids (Cnidaria: Hydrozoa) associated to a subtropical Sargassum cymosum (Phaeophyta: Fucales) bed

Hydroids are broadly reported in epiphytic associations from different localities showing marked seasonal cycles. Studies have shown that the factors behind these seasonal differences in hydroid richness and abundance may vary significantly according to the area of study. Seasonal differences in epiphytic hydroid cover and richness were evaluated in a Sargassum cymosum C. Agardh bed from Lazaro beach, at Ubatuba, Brazil. Significant seasonal differences were found in total hydroid cover, but not in species richness. Hydroid cover increased from March (early fall) to February (summer). Most of this pattern was caused by two of the most abundant species: Aglaophenia latecarinata Allman, 1877 and Orthopyxis sargassicola (Nutting, 1915). Hydroid richness seems to be related to S. cymosum size but not directly to its biomass. The seasonal differences in hydroid richness and algal cover are shown to be similar to other works in the study region and in the Mediterranean. Seasonal recruitment of hydroid species larvae may be responsible for their seasonal differences in algal cover, although other factors such as grazing activity of gammarid amphipods on S. cymosum must be taken into account.

Factors influencing temporal variation of a Sargassum filipendula (Phaeophyta: Fucales) bed in a subtropical shore

In the present study, we evaluate the influence of biotic and abiotic factors on temporal fluctuations of Sargassum filipendula in a subtropical shore. Monthly algal samples, abiotic components, amphipod grazer density, and epiphyte biomass were obtained from a Sargassum bed in south-eastern Brazil. Density of S. filipendula fronds decreased during the sampling period, whereas dry mass was more constant, although with a noticeable reduction in the warmer months. Hypnea musciformis was the most frequent epiphyte on S. filipendula, occurring in all sampling periods, although with significant temporal variation. Sargassum filipendula density and dry mass were both influenced by epiphyte dry mass, temperature, and amphipod grazers. Sargassum filipendula biomass negatively influenced total epiphyte biomass, whereas H. musciformis biomass was positively influenced by phosphate, nitrite, and S. filipendula density and negatively influenced by S. filipendula dry mass and amphipod grazer abundance. Algal temporal fluctuations can be related to local abiotic and biotic factors, but the variation observed for S. filipendula and its epiphytes suggest that these factors have quite distinct effects for these algae.

Influence of a narrow depth gradient and season on the morphology, phenology, and epibiosis of the brown alga Sargassum cymosum

Temporal and spatial fluctuations of environmental parameters are normally assigned as causes of variations in morpho-phenological characters of seaweeds and in their epibionts, but formal tests of such hypotheses are lacking, especially in narrowgradients. The present study evaluated the influence of a very small depth gradient ( 1 to 3 m) and of subtle seasonality characteristic of tropical areas on morpho-phenological traits and on the occurrence of sessile epiphytic organisms using a controlled orthogonal sampling design in a sublittoral population of the tropical brown alga Sargassum cymosum. Four temporal samples were obtained over a one-year period at three depths using nine replicates. The wet weight, maximum length, number of primary and secondary branches, and proportion of secondary branches with receptacles were recorded. Epibiosis was estimated by visual evaluation of percentage cover on secondary branches. Algal morphology varied as a function of the period of the year (weaker effect) and depth (stronger effect) but in different ways for each variable analysed. In general, fronds tended to be shorter, heavier, and more ramified in shallower areas. In relation to time, the morphological characters tended mostly to present higher values in January (summer) andlor April (autumn). Frequency of receptacles did not depend on algal morphology and depth at all but varied in time, although only in the deepest area. Epibiosis also did not depend on algal morphology but varied in relation to time (stronger effect) and, to a lesser extent, depth (weaker effect). The effect of time upon epibiosis also depended on the biological group analysed. These data support the hypothesis that algal morphology varies in relation to period of the year and depth, even under small temporal and spatial environmenal gradients.

Influence of environmental factors on benthic macroinvertebrate communities of urban streams in Vereda habitats, Central Brazil

AIM: Veredas and the aquatic and semi-aquatic communities play a key role in watershed protection in the Cerrado Biome. Information about the effects of physical and chemical variables and habitat integrity on benthic communities has been increased in recent years; however, there is no study evaluating the influence of urbanization on macroinvertebrates of Vereda streams. Thus, improving the knowledge of the relationship between abiotic properties and benthic fauna is very important for understanding the functioning of ecological processes and health of aquatic ecosystems. This study investigated the influence of physical and chemical variables on benthic macroinvertebrate communities along a gradient of anthropogenic disturbance in four Vereda streams in Uberlândia (MG), one in a preserved area and three in the urban area; METHODS: samplings were collected during the dry and rainy seasons; RESULTS: principal component analysis separated the stream in the preserved area from those in the urban area by having lower values of BOD, COD, sediment size, conductivity, detergents, pH, deposited solids and total dissolved solids. Pollution sensitive groups (e.g., Ephemeroptera and Trichoptera) were associated to the stream in the preserved area, and more tolerant groups (e.g., Chironomidae and Oligochaeta) had greater abundance in the streams of the urban area. Canonical Correspondence Analysis indicated that dissolved oxygen, conductivity, BOD, oil and grease, and turbidity explained 56% of the variance in the distribution and abundance of macroinvertebrates; CONCLUSIONS: Benthic communities of Vereda streams in urban areas in the Cerrado Biome seem to be highly affected by human activities that increase water organic pollution and sedimentation.

Biologia populacional das espécies de Ampithoidae (Crustacea, Amphipoda) associadas a Sargassum filipendula (Phaeophyta, Fucales) na Praia da Fortaleza, Ubatuba, São Paulo, Brasil

The population biology of three species of the family Ampithoidae ( Ampithoe ramondi , Cymadusa filosa e Sunampithoe pelagica ) associated with Sargassum filipendula at Fortaleza beach, northern coast of Sao Paulo state was investigated from June 2000 to May 2001. The amphipods were identified, counted and separated in size classes through a nested sieve set. Month hystograms were obtained for juveniles, males and females. The ampithoid sex ratio was determined monthly. The reproductive biology of the species was evaluated by the relative frequency of ovigerous females, fecundity, average egg volume and correlation analysis between head lengh of ovigerous females and number of eggs in its brood pouch. Ampithoe ramondi was the most abundant species. The higher densities of the three species occurred in spring and summer. The sex ratio presented a significant difference from 1:1 only for A. ramondi (1:1.2; x 2 = 4.37; g.l. = 1; p < 0.05). Ovigerous females were registered for almost all the sampling periods. A positive correlation between the female head lengh and the number of eggs were only registered for A. ramondi (r² = 0.27; p < 0.05; n = 33). Cymadusa filosa showed the greatest fecundity and egg volume.

Small-scale experimental contamination with diesel oil does not affect the recolonization of Sargassum (Fucales) fronds by vagile macrofauna

Coastal regions are subject to various forms of environmental impacts, such as spills of crude oil and associated products, with a wide range of effects on benthic biodiversity. This study characterized the patterns of recolonization of the macrofauna associated with the brown alga Sargassum cymosum(C. Agardh), on fronds contaminated by diesel oil in a small-scale field experiment. We collected 40 fronds of S. cymosum from an algal bed in southeastern Brazil and defaunated each frond by immersion in fresh water. Half of the fronds were then immersed in seawater (control group) and the other half in a mixture of 50% diesel oil and 50% seawater (impacted group). The test fronds were returned to the algal bed, and natural recolonization took place over a period of 12 days. Samples of the vagile macrofauna were taken randomly at three-day intervals over the course of the recolonization period. No significant differences in the densities of most taxa were found between the impact treatment (IG) and control treatment (CG). At the end of the recolonization period (day 12), the faunal composition of the treated fronds was very similar to the natural conditions, indicating a high rate of community recovery and suggesting that benthic associations can be rather resilient to diesel-oil impacts on a small scale.

Epiphytic hydroids (Cnidaria, Hydrozoa) contribute to a higher abundance of caprellid amphipods (Crustacea, Peracarida) on macroalgae

Habitat complexity is an important factor structuring macroinvertebrate communities on macrophytes, and epiphytic hydroids may offer additional habitats for the epifauna. Caprellids are known to benefit from the association with hydroids, but it is unclear if epiphytic hydroids affect their abundance. In this study, we investigated if caprellid abundance is related to epiphytic hydroid abundance on Sargassum cymosum, and whether this is related to caprellids’ clinging behavior. We found that hydroid abundance had a positive effect on caprellid abundance, irrespective of species, sex, developmental and reproductive stages of caprellids, with the exception of Caprella scaura that present maternal care behavior. Experiments also showed that caprellids are more abundant on fronds of Sargassum with hydroids. Moreover, juvenile caprellids prefer to cling directly to hydroids and also prefer portions of the alga with hydroids attached. Our results indicate that epiphytic hydroids add structural complexity to macroalgae, favoring the occurrence of caprellids. However, this effect may be conditioned by the reproductive behavior of caprellid species, since hydroids are particularly important for juveniles by offering suitable structures for their small pereopods to grasp. This, in turn, may indirectly benefit adult caprellids, contributing to their choice of habitats that favor the performance of their juveniles.