Rafel Coma

Benthic suspension feeders: their paramount role in littoral marine food webs.

In recent years, particular attention has been paid to coupling and energy transfer between benthos and plankton. Because of their abundance, certain benthic suspension feeders have been shown to have a major impact in marine ecosystems. They capture large quantities of particles and might directly regulate primary production and indirectly regulate secondary production in littoral food chains. Suspension feeders develop dense, three-dimensional communities whose structural complexity depends on flow speed. It has been postulated that these communities can self-organize to enhance food capture and thus establish boundary systems capable of successfully exploiting a less structured system, namely, the plankton.

LONG‐TERM ASSESSMENT OF TEMPERATE OCTOCORAL MORTALITY PATTERNS, PROTECTED VS. UNPROTECTED AREAS

Coastal marine protected areas (MPAs) are usually established with an aim to protect areas of special ecological value. However, protected areas tend to attract more tourism and associated recreational activities, thereby exposing the biota to new risks such as high diving activity. The effects of these drawbacks are still little known for low-dynamic systems such as one of the most characteristic and fragile Mediterranean communities, the coralligenous community. Mortality rates were assessed in both heavily dived and lightly dived areas to evaluate the effect of diving on the survival of the gorgonian Paramuricea clavata. The study was designed to distinguish human-induced causes from natural causes of gorgonian mortality and to provide criteria for sustainable management of protected areas. We examined total and partial mortality of adult colonies (>10 cm in height) at four locations, two each representing one of the two situations, heavily dived (MPA) and lightly dived (control), annually over a 9-yr ...

Prey capture by a benthic coral reef hydrozoan

Abstractu2002The natural diet and prey abundance of the benthic coral reef hydrozoan Nemalecium lighti, a common tropical species, were studied by analysing the gastrovascular contents of polyps. Prey capture was estimated from 10 samples collected at 3-h intervals during a single diel cycle (1–2 September, 1995) in the San Blas Islands (Panamá). Prey size ranged from 5 to 550u2004μm, with invertebrate larvae being the main contributor to the diet of the species. Prey items were found in 56–88% of the polyps over the entire diel cycle. Gastrovascular contents varied between 0.93 and 2.13 prey items per polyp. These capture incidences are among the highest reported for cnidarian species. Such rates would allow for high production rates for Nemalecium lighti, consistent with reports of the species’ fast growth and high reproduction rates. The observations suggest that some hydrozoans may be active heterotrophic components in coral reef ecosystems.

Stable symbionts across the HMA-LMA dichotomy: low seasonal and interannual variation in sponge-associated bacteria from taxonomically diverse hosts

Marine sponges host bacterial communities with important ecological and economic roles in nature and society, yet these benefits depend largely on the stability of host-symbiont interactions and their susceptibility to changing environmental conditions. Here, we investigated the temporal stability of complex host-microbe symbioses in a temperate, seasonal environment over three years, targeting sponges across a range of symbiont density (high and low microbial abundance, HMA and LMA) and host taxonomy (six orders). Symbiont profiling by terminal restriction fragment length polymorphism analysis of 16S rRNA gene sequences revealed that bacterial communities in all sponges exhibited a high degree of host specificity, low seasonal dynamics and low interannual variability: results that represent an emerging trend in the field of sponge microbiology and contrast sharply with the seasonal dynamics of free-living bacterioplankton. Further, HMA sponges hosted more diverse, even and similar symbiont communities than LMA sponges and these differences in community structure extended to core members of the microbiome. Together, these findings show clear distinctions in symbiont structure between HMA and LMA sponges while resolving notable similarities in their stability over seasonal and inter-annual scales, thus providing insight into the ecological consequences of the HMA-LMA dichotomy and the temporal stability of complex host-microbe symbioses.

Role of evolutionary and ecological factors in the reproductive success and the spatial genetic structure of the temperate gorgonian Paramuricea clavata.

Dispersal and mating features strongly influence the evolutionary dynamics and the spatial genetic structure (SGS) of marine populations. For the first time in a marine invertebrate, we examined individual reproductive success, by conducting larval paternity assignments after a natural spawning event, combined with a small-scale SGS analysis within a population of the gorgonian Paramuricea clavata. Thirty four percent of the larvae were sired by male colonies surrounding the brooding female colonies, revealing that the bulk of the mating was accomplished by males from outside the studied area. Male success increased with male height and decreased with increasing male to female distance. The parentage analyses, with a strong level of self-recruitment (25%), unveiled the occurrence of a complex family structure at a small spatial scale, consistent with the limited larval dispersal of this species. However, no evidence of small scale SGS was revealed despite this family structure. Furthermore, temporal genetic structure was not observed, which appears to be related to the rather large effective population size. The low level of inbreeding found suggests a pattern of random mating in this species, which disagrees with expectations that limited larval dispersal should lead to biparental inbreeding. Surface brooding and investment in sexual reproduction in P. clavata contribute to multiple paternity (on average 6.4 fathers were assigned per brood), which enhance genetic diversity of the brood. Several factors may have contributed to the lack of biparental inbreeding in our study such as (i) the lack of sperm limitation at a small scale, (ii) multiple paternity, and (iii) the large effective population size. Thus, our results indicate that limited larval dispersal and complex family structure do not necessarily lead to biparental inbreeding and SGS. In the framework of conservation purposes, our results suggested that colony size, proximity among colonies and the population size should be taken into consideration for restoration projects.

Quantification of sexual reproduction in the marine benthic hydroid Campanularia everta

Campanularia everta is an epiphytic hydroid that may form dense populations on the macroalga Halimeda tuna. The main objects of this study were to quantify sexual reporduction and estimate sexual reproductive output of this hydroid. Sexual reproduction occurred from mid-October to mid-December 1991 along the Spanish Mediterranean coast. During this period, male and female colonies formed gonangia. Four oocytes mature in each female gonangium, and embryonic development starts probably after internal fertilization occurs. Planulae complete their development within a mucus sheath attached to the top of the gonotheca (acrocyst). Eight successive gonangia with a life-span of ≈1 wk each were formed over a 2 mo period. The fertile period was characterized by high initial production of gonangia followed by a progressive decline resulting from a decrease both in the number of fertile colonies and in the gonangia density of fertile colonies. Annual production was estimated at ≈42000 gonangia m-2, representing 83000 oocytes m-2. The high fertilization rates observed (77 to 100%) yielded a minimum production of 64000 planulae m-2. Reproduction in C. everta is characterized by: (1) a high number of larvae produced m-2; (2) formation and gradual release of larvae throughout the sexual reproduction period; (3) direct formation of planulae with no intermediate medusa stage; (4) low dispersive ability of the planula. All these mechanisms are part of a reproductive strategy designed to ensure the permanence of the population in its habitat.

The Dynamic Core Microbiome: Structure, Stability And Resistance

The long-term stability of microbiomes is crucial as the persistent occurrence of beneficial microbes and their associated functions ensure host health. Microbiomes are highly diverse and dynamic, but are they complex to the point of being impossible to understand? We present an approach that while embracing this complexity it allows to identifying meaningful patterns: the dynamic core microbiome. We study the structure, dynamics and stability of microbiomes belonging to six marine sponges sampled monthly over three years. We show that microbiome temporal stability is not determined by the diversity of their microbial assemblages, but by the abundance density of those microbes that conform their core microbiome. High-density cores confer hosts resistance against the establishment of occasional taxa to which sponges are constantly exposed through their filter-feeding activities. The core microbial interaction network consisted of complementary members interacting weakly with a dominance of commensal and amensal interactions that have likely coevolved to maintain host functionality and fitness.

General Ecological Aspects of Anthozoan-Symbiodinium Interactions in the Mediterranean Sea

The aim of this chapter is to provide a general overview of the main ecological aspects of Anthozoan-Symbiodinium mutualisms in the Mediterranean Sea. There are reports of at least twelve species of symbiotic anthozans in the basin. These anthozoans establish symbiotic relations with Symbiodinium Temperate A and B2 (Symbiodinium psygmophilum), corresponding to the only two species of Symbiodinium described in the region. A synthesis of the trophic and biochemical aspects of the interaction between Symbiodinum and their cnidarian hosts is given to contribute to the understanding of the mechanisms that maintain this special association. Finally, current knowledge about the ecological importance of this interaction in engineering species is examined. This review is framed to highlight the ecological importance of this symbiotic relationship in ecosystem construction and maintenance on an enclosed, temperate marine basin.