Marine Biology

Each of the few known life-history strategies (e.g., r/K and parity [semelparity and iteroparity]), is a composite stratagem, signified by co-evolved sets of trade-offs with stochastically distributed variations that do not form novel structured strategies. Tracking the demographic traits of 81 Botryllus schlosseri (a marine urochordate) colonies, from birth to death, we revealed three co-existing novel life-history strategies in this long-standing laboratory-bred population, all are bracketed through colonial fission (termed NF, FA and FB for no fission, fission after and fission before reaching maximal colony size, respectively) and derived from organisms maintained in a benign, highly invariable environment. This environment allows us to capture the strategists’ blueprints and their net performance through 13 traits, each branded by high within-strategy variation. Yet, six traits differed significantly among the strategies and, in two, the FB was notably different. These results ...

When it comes to aging, some colonial invertebrates present disparate patterns from the customary aging phenomenon in unitary organisms, where a single senescence phenomenon along ontogeny culminates in their inevitable deaths. Here we studied aging processes in 81 colonies of the marine urochordate Botryllus schlosseri each followed from birth to death (over 720 days). The colonies were divided between three life history strategies, each distinct from the others based on the presence/absence of colonial fission: NF (no fission), FA (fission develops after the colony reaches maximal size), and FB (fission develops before the colony reaches maximal size). The study revealed recurring patterns in sexual reproductive statuses (hermaphroditism and male-only settings), colonial vigor, and size. These recurring patterns, collectively referred to as an Orshina, with one or more 'astogenic segments' on the genotype level. The combination of these segments forms the Orshina rhythm. E...

Within the COST action EMBOS (European Marine Biodiversity Observatory System) the degree and variation of the diversity and densities of soft-bottom communities from the lower intertidal or the shallow subtidal was measured at 28 marine sites along the European coastline (Baltic, Atlantic, Mediterranean) using jointly agreed and harmonized protocols, tools and indicators. The hypothesis tested was that the diversity for all taxonomic groups would decrease with increasing latitude. The EMBOS system delivered accurate and comparable data on the diversity and densities of the soft sediment macrozoobenthic community over a large-scale gradient along the European coastline. In contrast to general biogeographic theory, species diversity showed no linear relationship with latitude, yet a bell-shaped relation was found. The diversity and densities of benthos were mostly positively correlated with environmental factors such as temperature, salinity, mud and organic matter content in sedimen...

Coastal ecosystems are highly complex and driven by multiple environmental factors. To date we lack scientific evidence for the relative contribution of natural and anthropogenic drivers for the majority of marine habitats in order to adequately assess the role of different stressors across the European seas. Such relationship can be investigated by analysing the correlation between environmental variables and biotic patterns in multivariate space and taking into account non-linearities. Within the framework of the EMBOS (European Marine Biodiversity Observatory System) programme, hard bottom intertidal communities were sampled in a standardized way across European seas. Links between key natural and anthropogenic drivers and hard bottom communities were analysed using Boosted Regression Trees modelling. The study identified strong interregional variability and showed that patterns of hard bottom macroalgal and invertebrate communities were primarily a function of tidal regime, nutr...

Examining how variability in population abundance and distribution is allotted among different spatial scales can inform of processes that are likely to generate that variability. Results of studies dealing with scale issues in marine benthic communities suggest that variability is concentrated at small spatial scales (from tens of centimetres to few metres) and that spatial patterns of variation are consistent across ecosystems characterized by contrasting physical and biotic conditions, but this has not been formally tested. Here we quantified the variability in the distribution of intertidal rocky shore communities at a range of spatial scales, from tens of centimetres to thousands of kilometres, both in the NE Atlantic and the Mediterranean, and tested whether the observed patterns differed between the two basins. We focused on canopy-forming macroalgae and associated understorey assemblages in the low intertidal, and on the distribution of Patella limpets at mid intertidal leve...

1. Coastal reefs are highly diverse marine ecosystems that in many regions suffer today from growing pressures by human activities. Among the most highly-stressed are those found in the Levantine basin (south-eastern Mediterranean Sea). The Levant represents the trailingedge of distribution of native species where they are exposed to the most extreme temperature and salinity conditions, and the region is also fast-warming and exposed to a great many alien species and strong fishing pressure. In this study, the ecological state of reefs in the southeastern Levant was assessed quantitatively (including inside a small marine reserve) using current, extensive, survey data with reference to anecdotal historical information on their more pristine past. 2. The results of very extensive subtidal community surveys that were conducted in north Israel indicate that reefs in this area are currently dominated by turf-forming algae and aliens, and sustain low numbers of top predators. Specifically, it was found that on these Levant reefs: (1) commercial species represent a very small part of the fish assemblage (except inside the reserve); (2) alien species constitute a considerable portion (23-44%) of the fish assemblage (including in the reserve) and 95-99% of epi-benthic molluscs, including inside the marine reserve; and (3) turf barrens are the dominant substrate cover, while cover of native brown algae canopy is limited to small patches occurring only during winter and spring. 3. These findings suggest that the Levant reefs have been highly transformed by overfishing and alien invasions, and probably also climate change, and that even well managed marine reserves had little effect on alien species presence. From a biogeographic-conservation perspective, as both warming and bioinvasions continue in the Mediterranean, it is expected that this degraded reef state will gradually advance westward. Alleviating fishing pressure with marine reserves might make the reefs more resilient to these regional pressures, but alien invaders will remain a dominant feature in the system. Therefore, a more realistic conservation target might be the preservation or restoration of ecosystem functions rather than the original native biodiversity.

Your collection marking 150 years of Nature (go.nature.com/3481arj) makes no mention of a contribution to your first issue concerning the Suez Canal, which also celebrates its 150th anniversary this month. A letter to the editor suggested that the canal developers could have flooded Egypt's Lake Timsah, through which the canal passes, with fresh water from the Nile to render the desert fertile (see T. Login Nature 1, 24; 1869). The Suez Canal is one of the world's greatest vectors for invasive marine species, conveying them from the Red Sea to the Mediterranean Sea in a process known as Lessepsian migration (named after the canal's chief developer, Ferdinand de Lesseps). This damage to the Mediterranean's ecology has affected human health and economy (see B. S. Galil et al. Biol. Invasions 17, 973-976; 2015). Login's idea, which preceded the concept of biological invasion, has since been largely forgotten. In our view, it would be worth revisiting and adapting to prevent further introductions as the canal expands, for example by forming freshwater and/or hypersaline barriers. The latter could be recreated using brine from Egypt's new desalination plants to increase the salinity of the Bitter Lakes that lie farther south along the canal.

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The use of tributyltin (TBT)-based antifouling paints is unregulated in Israel, and levels of contamination are high along the Mediterranean coastline there. This is indicated by concentrations of butyltins found in the tissue, and by irnposex in the whelks Strarnonita haemastoma and Hexaplex trunculus. Both the old (since 1974) and new (since late 1995) marinas we studied are hotspots of pollution. Imposex indices were very high at the old manna (RPSI > 100, VDSI 4 to 5); all female H. trunculus and some S. haemastoma were sterile within a dlstance of ca 1 km from it. The new marina offered a unique opportunity to witness the rapid and intense response of the whelks to TBT pollution in an open coastline. Despite a marked decrease in levels of contarnmation at distances of 1 to 2 km from both marinas, there were nevertheless detectable levels of butyltins sufficient to cause imposex in reference sites far from high shipping activity. There is evidence that TBT contamination affects abundance and relatlve growth rates, of male and female, of the 2 whelks around the marinas. Differences in biological response to TBT were observed between the 2 whelk species: S. haemastoma had higher levels of organotins than H. trunculus in most study sites, which may be related to different sensitivity or accumulation rates. In S. haemastorna a male-biased sex ratio was revealed around the old Tel Aviv marina, which may be derived from either female mortality or from a complete sex change in some females. Further development of marinas at coastal resorts is undesirable, certainly in the absence of regulations limiting the use of TBT-based antifoulants, and the establishment of such regulations is highly recommended.

Biological invasions pose a great threat to the integrity of natural communities. Some invasive species demonstrate a population explosion shortly after arrival while in other cases a prolonged lag between arrival and population outbreak is evident. This paper describes a case of a prolonged lag and explores the possible mechanism for this lag. The Red Sea mussel Brachidontes pharaonis, a Lessepsian migrant, was first recorded in the Mediterranean seven years after the opening of the Suez Canal in 1869. Since then it spread along the Israeli coast and as far northwest as Sicily. Studies conducted in the late 1970s, when B. pharaonis was still rare, predicted that it would not establish dense populations along the Israeli coast and would not outcompete the indigenous mussel Mytilaster minimus, although it has strong negative effects on survival and growth of the native species. It was attributed to the invader's low intrinsic rate of increase relative to that of the native species, and to strong density-independent mortality generated by exposure to high wave action and sedimentation. In contrast to these predictions, we found massive formations of B. pharaonis beds after lag of about 120 years. We looked for distributional patterns that may explain this lag and found no south-north gradient but a strong habitat-dependent colonization. Most apparent are dense B. pharaonis mussel beds (density >300 per 100 cm 2 ) on rocky platforms where mussel beds were absent in the past. These platforms lack the vermetid rim that is typical to this formation. In platforms protected by a biogenic rim, sediment accumulation is high and perennial algae flourish. None of the mussel species form beds in such habitats. We suggest that the delayed formation of B. pharaonis beds along the Israeli coast is a consequence of a recent shift in habitat conditions on some platforms. It is possible that receding of the biogenic rim at the edge of these platforms allowed more effective washing, reduced sediment accumulation, and reduced perennial algae cover making platforms more suitable for the mussels. Lower density-independent mortality allowed B. pharaonis to dominate on such platforms over the indigenous species. On beachrock, a habitat previously dominated by M. minimus, we recorded a rapid shift in numerical domination to B. pharaonis (from 1 : 7 to 1.4 : 1 Brachidontes/Mytilaster individuals) over a period of 4 years (1995)(1996)(1997)(1998)(1999). This is probably a result of saturation of the habitat by B. pharaonis recruits originating from the established populations on platforms. Salinity changes and a potential genetic shift may also have contributed to the invasive mussel outbreak.

In this study, we test in southern New Zealand a conceptual model of food web linkage that is seascape dependent, which can explain some of the variability in rocky shore community structure among sites and coasts. Using a comparative-experimental approach at local and distant sites we demonstrate that mobile subtidal predators (fish and crabs) can exert strong predation pressure on small mussels in the low tidal zone, but only in sites where the seascape includes subtidal reefs. On intertidal benches with adjacent subtidal reefs (ϩSR), 60-100% of small (5-15 mm) transplanted mussels were removed within a day from experimental tiles on the low shore when unprotected from predation, compared to fully caged controls that had approximately 100% survival over several months. In partial cages that exclude fish but not crabs, survivorship was intermediate. In contrast, on benches without subtidal reefs (ϪSR) 40-100% of mussels survived for months, even if unprotected. This difference is expressed in lower cover (0-60%) of mussels on rocks at ϩSR benches compared to ϪSR benches (70-99%). The central to northern west coast of the South Island is composed mostly of ϪSR benches, and predation on small mussels there was low and similar to the ϪSR benches on the east coast, whereas the ϩSR benches on the east coast had much greater predation. This contrasts to other studies in New Zealand that examined only predation on larger mussels by seastars and concluded that predation is strong on the west coast and weak on the east coast. Excluding large predators from low-shore areas with new recruits for a year in one ϩSR site showed longer-term predation effects on their abundance and cover. Short-term sampling at the east coast sites showed that mussel settlement was greater in ϪSR compared to ϩSR sites, providing some evidence that seascapes may also affect settlement. Overall, predation depended on the local seascape and ultimately affected community structure via suppression of effective recruitment rates. This study emphasizes the importance of predation on early life stages of basal species and the influence of seascapes on top-down interactions between subtidal predators and their intertidal prey.

The supply of larvae to the shore is important for population replenishment and intertidal community dynamics but its variability at most scales is not well understood. We tested the relationship between nearshore mussel larval abundance and intertidal settlement rates over several years at multiple spatiotemporal scales in Oregon and New Zealand. Abundance of competent larvae nearshore and intertidal recruitment rates were simultaneously quantified using collectors mounted at different depths on moorings 50-1100 m from shore, and at adjacent rocky intertidal sites. Total mussel larval abundance and oceanographic conditions were also measured in some locations. At all scales, abundance of nearshore mussel larvae was unrelated to intertidal recruitment rates. In the intertidal, patterns of mussel recruitment were persistent in space, with sites of consistently high or low recruitment. In contrast, nearshore competent larval abundance showed generally similar abundances among sites except for a high, and spatiallyinconsistent, variability in Oregon during 1998 only. On moorings, recruitment tended to be greater on midwater collectors than shallower or deeper. Finally, on moorings larval abundance in traps and recruitment on collectors was unrelated. These results suggest that (1) among sites, the size of the nearshore larval pool is relatively uniform while onshore recruitment varies and is unrelated to larval abundance, (2) temporal variability in nearshore larval availability is not strongly expressed onshore, (3) vertical stratification of competent larvae nearshore is strong and may influence transport and recruitment, and (4) within-coast variability in onshore recruitment is strongly driven by processes occurring locally within the surf zone that need to be studied to understand coastal recruitment dynamics.

The mussel Brachidontes pharaonis, which invaded the Mediterranean from the Red Sea about 120 years ago, has recently become abundant in many midlittoral and some infralittoral rocky habitats along the Israeli rocky shore. We investigated the influence of B. pharaonis, as a novel prey, on the foraging patterns of the large whelk Stramonita haemastoma in the field, and examined food preferences in the laboratory. S. haemastoma has shifted from indigenous species to feeding on the novel mussel when abundant. The whelk prefers to prey upon the invasive mussel over all indigenous species offered (e.g. barnacles and mussels), probably due to its larger size. In the midlittoral zone, the foraging activity of S. haemastoma is considerably low even where refuges are readily available (incisioned-rocks) and food density is high (mainly B. pharaonis). Higher proportions of whelks are actively foraging in the infralittoral zone but usually on smaller prey, mostly barnacles. We suggest that this differential foraging activity in the two zones is related to the degree of exposure to wave action. The midlittoral is inherently more exposed to wave action than the infralittoral, where sea conditions are more benign and the whelks may enjoy longer activity periods. # Marine Environmental Research 54 www.elsevier.com/locate/marenvrev 0141-1136/02/$ -see front matter # 2002 Elsevier Science Ltd. All rights reserved. P I I : S 0 1 4 1 -1 1 3 6 ( 0 2 ) 0 0 0 9 6 -X

Predicting how fine-scale temperature variation will affect the spatial distribution and temporal stability of species and communities under climate change View project MarCons: Advancing marine conservation in the European and contiguous seas (COST Action 15121) View project

The rocky littoral is a highly stressed but species rich environment in which adaptive trade-offs underlie the specialization that permits habitat partitioning by closely-related species. Habitat partitioning by prey species is generally attributed to differential tolerances to physiological stresses and competition for resources. Partitioning by predators is, however, less understood and also mainly related to thermal tolerance. We test the hypothesis that differential biomechanical and behavioral adaptations to wave action can result in habitat partitioning of mobile predators using 2 Mediterranean whelks. Stramonita haemastoma is found mainly at wave-exposed habitats on lower midlittoral or shallow (1 to 3 m) subtidal rocks. By contrast, Hexaplex trunculus is found only subtidally in more quiescent littoral environments (shallow bays and lagoons or deeper in wave-exposed sites). Morphologically, S. haemastoma is squatter than H. trunculus and the ratio of its foot surface area to the maximum projected surface area of its shell is 35% higher, making S. haemastoma less prone to dislodgment by waves. Mechanically, at least a 2-fold higher force (12 N) is required to dislodge S. haemastoma from the substrate, probably due to its larger foot, because tenacity per foot area was similar between species. The feeding technique and foraging behavior of S. haemastoma is also adapted to life in high-energy environments. Higher feeding rates and much shorter prey handling time compared to H. trunculus allow this species shorter foraging bouts that reduce the risk of dislodgment and increase predation success in wave-exposed areas. H. trunculus thrives in low-flow habitats where food density is low compared to shallow subtidal rocks. This is compensated for by a broader diet than S. haemastoma, feeding on any available food item, including conspecifics, and by reducing adhesion when not feeding, thus saving energy. S. haemastoma is more adapted to survive desiccation conditions than H. trunculus, which may exclude the latter from intertidal habitats. Our findings suggest that habitat partitioning between the whelks is maintained mainly by a 'distinct preferences' mechanism that might be relevant for other benthic predatory species.

CITATIONS 16 READS 129 4 authors, including: Some of the authors of this publication are also working on these related projects: MarCons: Advancing marine conservation in the European and contiguous seas (COST Action 15121) View project European Marine Biodiversity Observatory Systems