Durvillaea Antarctica Research Articles

Asymmetric dispersal of southern bull-kelp (Durvillaea antarctica) adults in coastal New Zealand: testing an oceanographic hypothesis.

Coastal populations are often connected by unidirectional current systems, but the biological effects of such asymmetric oceanographic connectivity remain relatively unstudied. We used mtDNA analysis to determine the phylogeographic origins of beach-cast bull-kelp (Durvillaea antarctica) adults in the Canterbury Bight, a 180 km coastal region devoid of rocky-reef habitat in southern New Zealand. A multi-year, quantitative analysis supports the oceanographically derived hypothesis of asymmetric dispersal mediated by the north-flowing Southland Current. Specifically, 92% of beach-cast specimens examined had originated south of the Bight, many drifting north for hundreds of kilometres, and some traversing at least 500 km of ocean from subantarctic sources. In contrast, only 8% of specimens had dispersed south against the prevailing current, and these counter-current dispersers likely travelled relatively small distances (tens of kilometres). These data show that oceanographic connectivity models can provide robust estimates of passive biological dispersal, even for highly buoyant taxa. The results also indicate that there are no oceanographic barriers to kelp dispersal across the Canterbury Bight, indicating that other ecological factors explain the phylogeographic disjunction across this kelp-free zone. The large number of long-distance dispersal events detected suggests drifting macroalgae have potential to facilitate ongoing connectivity between otherwise isolated benthic populations.

Feeding preferences of the sandhopper Orchestoidea tuberculata: the importance of algal traits

Factors such as nutritional quality and the secondary metabolite content of food resources have been shown to influence the feeding behavior of herbivores in many marine habitats. For intertidal macroalgae consumers on sandy beaches, the influence of these factors on feeding behavior and the consequences on their performance is poorly understood. In this study, we evaluated the relationships of nutritional quality, chemical defenses (phlorotannins), and the structure of three macroalgal species that form the bulk of imported wrack subsidies to beaches in southern Chile, with the feeding behavior, absorption efficiency, and growth rate of the talitrid amphipod Orchestoidea tuberculata, one of the most abundant organisms in this environment. The amphipods preferred Durvillaea antarctica over Lessonia nigrescens and Macrocystis pyrifera when simultaneously offered fresh pieces of each alga. Similar results were observed when artificial food made of dry powdered algae of each species was provided, suggesting that the structure of these three algae did not influence preference. The performance of amphipods when reared on a diet of a single algal species matched feeding preferences; higher growth rates were observed in treatments with the preferred alga, D. antarctica. These results imply that D. antarctica is a superior food item for O. tuberculata when compared to L. nigrescens or M. pyrifera, and also that the alga’s intrinsic quality (i.e., not structure) may influence dietary preference in these consumers. The higher content of proteins and carbohydrates found in D. antarctica may explain why this macroalga represents better quality food for O. tuberculata. Phlorotannin content did not have obvious negative effects on diet choice or growth, as D. antarctica, the alga with greater content of these secondary metabolites, was preferred and associated with higher growth rates of O. tuberculata. However, it is necessary to emphasize that the low phlorotannins concentrations registered in the three macroalgae species examined in this study, may not have been sufficient to deter O. tuberculata. When the amphipods were fed with each alga individually, they consumed significantly higher quantities of D. antarctica, which suggests that O. tuberculata did not eat more to compensate for the lower nutritional quality of the other algal species in order to maintain growth. Nor was compensation for lower food quality achieved by increasing absorption efficiency. Our results imply that the composition of the macroalgae arriving on the beach can significantly affect the performance and subsequent life history traits of O. tuberculata and by extension other amphipod species.

Temporal and spatial distribution of floating objects in coastal waters of central–southern Chile and Patagonian fjords

Floating objects are suggested to be the principal vector for the transport and dispersal of marine invertebrates with direct development as well as catalysts for carbon and nutrient recycling in accumulation areas. The first step in identifying the ecological relevance of floating objects in a specific area is to identify their spatio-temporal distribution. We evaluated the composition, abundance, distribution, and temporal variability of floating objects along the continental coast of central–southern Chile (33–42°S) and the Patagonian fjords (42–50°S) using ship surveys conducted in austral winter (July/August) and spring (November) of the years 2002–2005 and 2008. Potential sources of floating items were identified with the aid of publicly available databases and scientific reports. We found three main types of floating objects, namely floating marine debris (mainly plastic objects and Styrofoam), wood (trunks and branches), and floating kelps ( Macrocystis pyrifera and Durvillaea antarctica). Floating marine debris were abundant along most of the examined transects, with markedly lower abundances toward the southern fjord areas. Floating marine debris abundances generally corresponded to the distribution of human activities, and were highest in the Interior Sea of Chiloé, where aquaculture activities are intense. Floating wood appeared sporadically in the study area, often close to the main rivers. In accordance with seasonal river run-off, wood was more abundant along the continental coast in winter (rainy season) and in the Patagonian fjords during the spring surveys (snow melt). Densities of the two floating kelp species were similar along the continental coast, without a clear seasonal pattern. M. pyrifera densities increased towards the south, peaking in the Patagonian fjords, where it was dominant over D. antarctica. Densities of M. pyrifera in the Patagonian fjords were highest in spring. Correlation analyses between the abundances of floating objects and the distance to the nearest sources were generally non-significant, suggesting that post-supply processes affect the distribution of the floating objects in the study region. The identification of several major retention zones supports this idea. Accumulation areas of floating objects appear to be more common in the fjord zones. In general, the results underscore the abundance of floating objects throughout the study region and the fact that floating marine debris sources are mostly local, whereas floating algae may be dispersed over greater distances. Future studies should focus on the ecological role of floating objects in biota dispersal and nutrient cycling.

Circumpolar dispersal by rafting in two subantarctic kelp-dwelling crustaceans

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 405:221-230 (2010) - DOI: https://doi.org/10.3354/meps08523 Circumpolar dispersal by rafting in two subantarctic kelp-dwelling crustaceans R. Nikula*, C. I. Fraser, H. G. Spencer, J. M. Waters Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand *Email: raisa.nikula@otago.ac.nz ABSTRACT: Long-distance oceanic rafting is frequently invoked as an explanation for broad geographic distributions of sedentary marine taxa, but evidence for this ecological process remains elusive. We explored empirically the potential of rafting as a dispersal mechanism by comparing circumpolar mtDNA variability in 3 codistributed subantarctic taxa: 2 direct-developing epifaunal crustacean species (Limnoria stephenseni, Parawaldeckia kidderi) and their macroalgal host (Durvillaea antarctica). A previous study of D. antarctica suggests that its subantarctic populations were established only postglacially, and we predict that the epifaunal invertebrates associated with it experienced a parallel island-colonization episode, facilitated by kelp-rafting. We generated and analysed mtDNA sequence data (cytochrome oxidase subunit I [COI] gene, >900 base pairs) from 89 L. stephenseni and 62 P. kidderi specimens and reanalysed previously published comparable data for D. antarctica. Both epifaunal species exhibited wide-scale circumpolar distributions of a single haplotype. Little sequence diversity was found within island samples, with the exception of P. kidderi in the Falkland Islands. The phylogeographic diversity and structuring of the invertebrates was very similar to that of their kelp host and consistent with a scenario of subantarctic recolonization and population expansion. The dependence of these otherwise non-dispersive crustaceans on macroalgal holdfasts for food and habitat, as well as the great abundance of D. antarctica adrift in the Antarctic Circumpolar Current (ACC), support rafting as their most plausible recolonization mechanism. We suggest that macroalgal rafting may explain similarities in the species composition of intertidal marine communities across the subantarctic. KEY WORDS: Rafting · Long-distance dispersal · Marine biogeography · Phylogeography · Macroalga · mtDNA · Peracarida · Durvillaea antarctica Full text in pdf format PreviousNextCite this article as: Nikula R, Fraser CI, Spencer HG, Waters JM (2010) Circumpolar dispersal by rafting in two subantarctic kelp-dwelling crustaceans. Mar Ecol Prog Ser 405:221-230. https://doi.org/10.3354/meps08523 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 405. Online publication date: April 29, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Nutrient and heavy metal content of edible seaweeds in New Zealand

The nutritional composition of four commercially available seaweeds, Macrocystis pyrifera, Undaria pinnatifida, Porphyra and Ecklonia radiata, was compared with six wild-harvested species, Ulva stenophylla, Porphyra, Ecklonia radiata, Durvillaea antarctica, Hormosira banksii and Undaria pinnatifida. In the wild-collected species, ash contents were high (19.8–26.6% dry weight). Carbohydrate content ranged from 45.4–66.9%, while protein varied from 6.1–32.7%. Some species had high levels of potassium (<71.2 g/kg) and calcium (<15.3 g/kg). Total arsenic concentrations were high in some species (<97 mg/kg), but the dominant forms were the organic arsenic compounds that are regarded as non-toxic. Inorganic arsenic was well below the New Zealand regulatory limit. The variation in proximate composition and mineral content was high among species collected at different times or locations and between different species. New Zealand's native and naturalized seaweeds are comparable to other edible seaweeds and would be a healthy addition to normal diets.

Interacting effects of copper, nitrogen and ultraviolet radiation on the physiology of three south Pacific kelps

Coastal ecosystems currently face multiple environmental impacts, such as nutrient loading, chemical contamination and enhanced ultraviolet (UV) radiation. Large kelps dominate many rocky shores worldwide and their capacity to handle environmental stress could have major consequences for these systems. The impacts of the interaction of copper (150 μg L–1), nitrate (350 μM) and short-term UV radiation on the physiological responses (photosynthetic activity, contents and anti-oxidant activity of phlorotannins) of three large kelps, Macrocystis pyrifera, Lessonia nigrescens and Durvillaea antarctica, from the coast of Chile were studied during a 2-week laboratory exposure. Macrocystis accumulated the most copper in its tissues, which decreased under nitrate-enriched conditions. Inhibition of photosynthetic activity by copper was observed in all three species (11–30%) after 12 days of incubation, with the strongest response in Lessonia. Nitrate enrichment mitigated the inhibitory effect of copper on photosynthesis in all three species. Soluble phlorotannin content decreased under copper and/or nitrate-enriched conditions with additional short-term UV exposure, particularly in Durvillaea, in which the strongest increase in the anti-oxidant activity of soluble phlorotannins was observed. Overall, the observed physiological responses reflect differences in morpho-functional processes and habitat characteristics of the three kelps and the importance of the interactions of multiple environmental factors.

Contemporary habitat discontinuity and historic glacial ice drive genetic divergence in Chilean kelp.

BackgroundSouth America's western coastline, extending in a near-straight line across some 35 latitudinal degrees, presents an elegant setting for assessing both contemporary and historic influences on cladogenesis in the marine environment. Southern bull-kelp (Durvillaea antarctica) has a broad distribution along much of the Chilean coast. This species represents an ideal model taxon for studies of coastal marine connectivity and of palaeoclimatic effects, as it grows only on exposed rocky coasts and is absent from beaches and ice-affected shores. We expected that, along the central Chilean coast, D. antarctica would show considerable phylogeographic structure as a consequence of the isolating effects of distance and habitat discontinuities. In contrast, we hypothesised that further south - throughout the region affected by the Patagonian Ice Sheet at the Last Glacial Maximum (LGM) - D. antarctica would show relatively little genetic structure, reflecting postglacial recolonisation.ResultsMitochondrial (COI) and chloroplast (rbcL) DNA analyses of D. antarctica from 24 Chilean localities (164 individuals) revealed two deeply divergent (4.5 - 6.1% for COI, 1.4% for rbcL) clades from the centre and south of the country, with contrasting levels and patterns of genetic structure. Among populations from central Chile (32° - 44°S), substantial phylogeographic structure was evident across small spatial scales, and a significant isolation-by-distance effect was observed. Genetic disjunctions in this region appear to correspond to the presence of long beaches. In contrast to the genetic structure found among central Chilean populations, samples from the southern Chilean Patagonian region (49° - 56°S) were genetically homogeneous and identical to a haplotype recently found throughout the subantarctic region.ConclusionsSouthern (Patagonian) Chile has been recolonised by D. antarctica relatively recently, probably since the LGM. The inferred trans-oceanic ancestry of these Patagonian populations supports the notion that D. antarctica is capable of long-distance dispersal via rafting. In contrast, further north in central Chile, the correspondence of genetic disjunctions in D. antarctica with long beaches indicates that habitat discontinuity drives genetic isolation among established kelp populations. We conclude that rafting facilitates colonisation of unoccupied shores, but has limited potential to enhance gene-flow among established populations. Broadly, this study demonstrates that some taxa may be considered to have either high or low dispersal potential across different temporal and geographic scales.

Algal populations controlled by fish herbivory across a wave exposure gradient on southern temperate shores

Consumers that forage across habitats can affect communities by altering the abundance and distribution of key species. In marine communities, studies of trophic interactions have generally focused on the effects of herbivorous and predatory invertebrates on benthic algae and mussel populations. However, large mobile consumers that move across habitats, such as fishes, can strongly affect community dynamics through consumption of habitat-dominating species, but their effects often vary over environmental gradients. On temperate rocky shores, herbivorous fishes are generally a small part of the fish fauna compared to the tropics, and there is sparse evidence that they play a major direct role in algal community dynamics, particularly of large brown algae that dominate many reefs. In New Zealand, however, a wide-ranging herbivorous fish, Odax pullus, feeds exclusively on macroalgae, including Durvillaea antarctica, a large low-intertidal fucoid reaching 10 m in length and 70 kg in mass. In four experiments we tested the extent of fish herbivory and how it was affected by algal canopy structure across a gradient of wave exposure at multiple sites. Exclusion experiments showed that fish impacts greatly reduced the cover and biomass of Durvillaea and that these effects decreased with increasing wave stress and algal canopy cover, effectively restricting the alga to exposed conditions. Almost all plants were entirely removed by fish where there was a sparse algal canopy in sheltered and semi-exposed sites, but there was significantly less grazing in exposed sites. Recruit Durvillaea beneath canopies were less affected by fish grazing, but they grew slowly. Successful natural recruitment, therefore, occurred almost exclusively on exposed shores outside canopies where many plants escaped severe grazing, and growth to maturity was far greater than elsewhere. Such large and direct impacts on the local and regional distribution of large brown algal populations by mobile vertebrate consumers are rare and were mediated by an environmental gradient and plant density, both of which interact with algal demographics. The study highlights that, even though herbivorous fish diversity may be low, the impacts of particular species may still be high, even in cool temperate waters where fish herbivory is usually considered to be minimal.

Spatial and temporal distribution of floating kelp in the channels and fjords of southern Chile

Numerous studies suggest that floating macroalgae contribute to population connectivity of the algae themselves as well as of associated organisms. In order to evaluate the importance of floating macroalgae for population connectivity in southern Chile we analysed their spatial and temporal distributions. We estimated the abundance of floating kelp in the Interior Sea of Chiloé and the Los Chonos Archipelago via ship surveys conducted during austral spring (November) and winter (July) of the years 2002–2005. Highest densities of floating kelp ( Macrocystis pyrifera and Durvillaea antarctica) were found during spring. Generally, the density of floating kelp was relatively low in areas with high supply of freshwater, and highest abundances were found in large channels opening to the open ocean. We suggest that this pattern is caused by the scarcity of natural kelp beds combined with rapid degradation of floating kelp in the interior fjords and by seaward surface outflow. The maximum densities of floating kelps were found in an area known to be an extensive convergence zone (i.e. estuarine front), which appears to act as a retention zone. In accordance with this distribution pattern, we propose that connectivity between local populations via floating kelp is higher in the outer channels with oceanic influence than in the inner fjords with high freshwater influx.

Settlement rates of macroalgal algal propagules: Cross‐species comparisons in a turbulent environment

The ability of propagules (fertilized eggs) of five species of fucoid algae (Hormosira banksii, Durvillaea antarctica, Cystophora torulosa from New Zealand, and Fucus gardneri and Pelvetiopsis limitata from Oregon, U.S.A.) to settle and attach was tested in a turbulent, stirred tank. The time taken to reach a steady state of settlement numbers varied between species and turbulence intensities. Normalized steady‐state (NSS) settlement numbers showed differences among species. A settlement model, based on principles invoked in the analysis of motion of bed sediments in rivers, was developed. The model indicates that the NSS settlement number depends on two parameters, a propagule Reynolds number and an entrainment function that represents the relative importance of the shear stress experienced by settled propagules and their submerged weight. The inability of this model to collapse the data for all species suggests that the stickiness of the propagules, due to their mucus coatings, plays a significant role in the settlement process. P. limitata (largest propagules) exhibited the least effective attachment to the substratum, whereas F. gardneri (second largest) and D. antarctica (smallest propagules) were the most effective at withstanding hydrodynamic forces that detach propagules. We also model the boundary layer above a flat‐bed, driven by linear water‐waves, using a skin‐friction drag coefficient and show that this study represents the lower end of the shear velocity u* range. However, these experiments capture the main region of variability in long‐term propagule attachment, and indicate that most of these fucoid species will have successful settlement only during calm conditions.

Occurrence of arsenic species in the seagrass Posidonia oceanica and in the marine algae Lessonia nigrescens and Durvillaea antarctica

The seagrass Posidonia oceanica from the Mediterranean coast and the brown algae Durvillaea antarctica and Lessonia nigrescens from the Chilean coast were analysed for total arsenic and for arsenic species. Arsenic species were extracted with water and measured by high-performance liquid chromatography–inductive coupled plasma mass spectrometry. Arsenite, arsenate, methylarsonate, dimethylarsinate, sulfonate sugar, sulphate sugar and phosphate sugar were analysed with an anion exchange column. Arsenobetaine, arsenocholine and glycerol sugar were separated with a cation exchange column. An extract of Fucus serratus was used to assign the arsenosugar peaks in the chromatograms from the sample extracts. In addition to the four common arsenosugars found in algae, inorganic arsenic was also measured in some samples, with the highest content found in L. nigrescens. The certified reference material (CRM) NIES no. 9 Sargassum fullvellum was analysed for quality assessment of total arsenic, and moreover, arsenosugars were also determined in this CRM.

GENETIC AND MORPHOLOGICAL ANALYSES OF THE SOUTHERN BULL KELP DURVILLAEA ANTARCTICA (PHAEOPHYCEAE: DURVILLAEALES) IN NEW ZEALAND REVEAL CRYPTIC SPECIES(1).

Many macroalgae exhibit considerable intraspecific morphological variation, but whether such variation reflects phenotypic plasticity or underlying genetic differences is often poorly understood. We quantified both morphological and genetic variation of 96 plants from seven field sites across eastern South Island, New Zealand, to assess genetic differences between morphotypes of the southern bull kelp Durvillaea antarctica (Cham.) Har. Consistent DNA sequence differentiation across mitochondrial, plastid, and nuclear loci was correlated with two broadly sympatric morphotypes: "cape" and "thonged." These ecologically, morphologically, and genetically distinct bull-kelp lineages were previously considered to be environmentally determined phenotypes with no underlying genetic basis. Interestingly, the sheltered "cape" lineage appears essentially genetically uniform across its South Island range, whereas the exposed "thonged" lineage exhibits marked phylogeographic structure across its range. Results suggest that D.antarctica in New Zealand comprises two reproductively isolated species.

Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum.

The end of the Last Glacial Maximum (LGM) dramatically reshaped temperate ecosystems, with many species moving poleward as temperatures rose and ice receded. Whereas reinvading terrestrial taxa tracked melting glaciers, marine biota recolonized ocean habitats freed by retreating sea ice. The extent of sea ice in the Southern Hemisphere during the LGM has, however, yet to be fully resolved, with most palaeogeographic studies suggesting only minimal or patchy ice cover in subantarctic waters. Here, through population genetic analyses of the widespread Southern Bull Kelp (Durvillaea antarctica), we present evidence for persistent ice scour affecting subantarctic islands during the LGM. Using mitochondrial and chloroplast genetic markers (COI; rbcL) to genetically characterize some 300 kelp samples from 45 Southern Ocean localities, we reveal a remarkable pattern of recent recolonization in the subantarctic. Specifically, in contrast to the marked phylogeographic structure observed across coastal New Zealand and Chile (10- to 100-km scales), subantarctic samples show striking genetic homogeneity over vast distances (10,000-km scales), with a single widespread haplotype observed for each marker. From these results, we suggest that sea ice expanded further and ice scour during the LGM impacted shallow-water subantarctic marine ecosystems more extensively than previously suggested.

Systematics and phylogeny of a new cryptic species of Diloma Philippi (Mollusca: Gastropoda: Trochidae) from a novel habitat, the bull kelp holdfast communities of southern New Zealand

The seven currently recognised New Zealand species in the gastropod genus Diloma Philippi, 1845 are an important component of New Zealand’s littoral biodiversity across a range of intertidal habitats. A new cryptic species in this genus (Diloma durvillaea, sp. nov.) is described largely on molecular grounds from exposed coasts of the South Island of New Zealand from Lyttelton south, as well as the Auckland Islands. The shell is very similar to D. arida (Finlay, 1926), differing subtly in having stronger spiral ribs and less extensive or no yellow spotting. Phylogenetic analysis of the mitochondrial cytochrome c oxidase I (COI) gene shows these two species are sister-taxa and are more distinct from each other (genetic distance 11.5%) than are the morphologically divergent sister-species D. subrostrata (Gray, 1835) and D. aethiops (Gmelin, 1791) (8.2%), also from New Zealand. The new species is found in a novel habitat for the genus, in the holdfasts and on the blades of the bull kelp, Durvillaea antarctica (Cham.) Har. (Phaeophyta), at the low-tide mark on exposed coasts, whereas D. arida occurs higher up on the shore, as well as in more sheltered situations.

Affiliation of the parasite Herpodiscus durvillaeae (Phaeophyceae) with the Sphacelariales based on DNA sequence comparisons and morphological observations

The phylogenetic affinities of the brown alga Herpodiscus durvillaeae, an obligate parasite of Durvillaea antarctica (Fucales, Phaeophyceae) endemic to New Zealand, were analysed using combined partial nuclear encoded ribosomal DNA (26S) and plastid encoded RuBisCO (rbcL) gene sequences. Results from phylogenetic analyses place this species within the order Sphacelariales. Molecular data were supported by two morphological features characteristic for the Sphacelariales sensu stricto: the presence of apical cells and the transitory blackening of the cell wall with sodium hypochlorite solution (‘Eau de Javel’). However, the strongly heteromorphic life history distinguishes H. durvillaeae from all other members of the Sphacelariales of which the life cycle is known. This variability in life history provides a new systematic character for the order and should be taken into account in any comprehensive systematic revision of the Sphacelariales.

Characterisation of wave-influenced macroalgal propagule settlement

Successful attachment of macrophyte propagules in the rocky intertidal zone requires that propagules actually arrive at the substrate (settlement). The analysis first considers the small-scale processes occurring at the propagule scale then places these results in the context of long timescale variability in wave forcing due to weather and climate. The non-dimensional scaling is developed in terms of a Particle Reynolds number, Re ⁎p, that depends on both flow and particle scales. Scaling for size, inertia and buoyancy are described in terms of the Re ⁎p. Settlement mechanics of several macrophyte species ( Durvillaea antarctica, Hormosira banksii and Cystophora torulosa) are compared using direct velocity measurements and placed in an environmental context using a twenty-year wave hindcast. The forcing is shown to be more closely linked to wave orbital speeds rather than breaker-driven phase speeds, and (negative) buoyancy has the greatest influence, identified through a Buoyancy Travel Ratio (BTR). Differences in these physical scales between the species are only moderate, suggesting supply, mucous and stickiness effects must be considered to fully resolve difference in success.

Evaluation of marine algae as a source of biogas in a two-stage anaerobic reactor system

The marine algae are considered an important biomass source; however, their utilization as energy source is still low around the world. The technical feasibility of marine algae utilization as a source of renewable energy was studied to laboratory scale. The anaerobic digestion of Macrocystis pyrifera , Durvillea antarctica and their blend 1:1 (w/w) was evaluated in a two-phase anaerobic digestion system, which consisted of an anaerobic sequencing batch reactor (ASBR) and an upflow anaerobic filter (UAF). The results show that 70% of the total biogas produced in the system was generated in the UAF, and both algae species have similar biogas productions of 180.4(±1.5) mL g −1 dry algae d −1 , with a methane concentration around 65%. The same methane content was observed in biogas yield of algae blend; however, a lower biogas yield was obtained. In conclusion, either algae species or their blend can be utilized to produce methane gas in a two-phase digestion system.

Recovery of Durvillaea antarctica (Durvilleales) inside and outside Las Cruces Marine Reserve, Chile.

We present the results for over two decades of monitoring on intertidal food-gatherers and the population of the low rocky shore dweller kelp Durvillaea antarctica, a short-distance disperser, inside and outside the no-take marine reserve, Estacion Costera de Investigaciones Marinas (ECIM), at Las Cruces, central Chile. It was hypothesized that protection of an initially extremely depleted population would recover by recolonizing first the no-take area and then adjacent non-protected (exploited) areas. We found that recovery of D. antarctica occurred slowly inside ECIM, with increase in density and biomass, of up to three orders of magnitude as compared to an adjacent non-protected area, which showed approximately 2-yr delay. These results suggest that the kelp population inside ECIM was likely regulated via intraspecific competition, which did not occur outside. Results showed no evidence for juvenile vs. adult density dependence other than a weak relationship for the central area of ECIM. These findings also suggest that the population recovery and cross-boundary seeding subsides affected the population dynamics. Understanding these dynamics may enhance management and conservation policies. Our work highlights the critical value of baseline and long-term comparative studies in marine no-take protected and non-protected areas for understanding how population processes respond to human and conservation practices.

Comparison of mechanical properties of four large, wave‐exposed seaweeds

Seaweeds have a simple structural design compared to most terrestrial plants. Nonetheless, some species have adapted to the severe mechanical conditions of the surf zone. The material properties of either tissue sections or the whole stipe of four wave-exposed seaweeds, Durvillaea antarctica, D. willana, Laminaria digitata, and L. hyperborea, were tested in tension, bending, and torsion. Durvillaea has a very low modulus of elasticity in tension (E(tension) = 3-7 MN·m(-2)) and in bending (E(bending) = 9-12 MN · m(-2)), torsion modulus (G = 0.3 MN · m(-2)) and strength (σ(b)rk = 1-2 MN · m(-2)), combining a compliable and twistable stipe "material" with a comparatively high breaking strain (ε(brk) = 0.4-0.6). In comparison, the smaller stipes of Laminaria have a higher modulus of elasticity in tension (E(tension) = 6-28 MN·m(-2)) and in bending (E(bending) = 84-109 MN·m(-2)), similar strength (σ(brk) = 1-3 MN·m(-2)), and a higher torsion modulus (G = 0.7-10 MN·m(-2)), combined with a lower breaking strain (ε(brk) = 0.2-0.3) than Durvillaea. Time-dependent, viscoelastic reactions were investigated with cycling tests. The tested species dissipated 42-52% of the loading energy in tension through plastic-viscoelastic processes, a finding that bears important ecological implications. Overall, there seems to be no correlation between single material properties and the size or habitat position of the tested seaweed species.

Co-management Policy Can Reduce Resilience in Traditionally Managed Marine Ecosystems

Best-practice environmental policy often suggests co-management of marine resources as a means of achieving sustainable development. Here we consider the impacts of superimposing co-management policy, in the form of territorial user rights for fishers over an existing traditional community-based natural-resource management system in Chile. We consider a broad definition of co-management that includes a spectrum of arrangements between governments and user groups described by different levels of devolution of power. We used participatory rural appraisal techniques and questionnaires to understand the mechanisms that underpin the traditional management system for the bull-kelp “cochayuyo” (Durvillaea antarctica). Traditional management was based on the allocation of informal access rights through a lottery system. This system was controlled by a complex web of traditional institutions that were shown to be successful in terms of equity and resilience. Using a similar approach, we analyzed the effects of superimposing a government-led co-management policy into this traditional system. Two major effects of the new policy were encountered. First, traditional institutions were weakened, which had negative effects on the levels of trust within the community and intensified conflict among users. Second, the management system’s adaptive capacity was reduced, thereby jeopardizing the ecosystem’s resilience. Our results suggest that the devolution of power to this kind of fisher community still has not reached the level required for fishers to legally address the local deficiencies of the Chilean co-management policy. Additionally, legal adjustments must be made to accommodate traditionally managed ecosystems that offer benefits comparable to those mandated under the formal policy. A fuller understanding of the interactions between co-management and traditional institutions can help us to identify ways to promote resilience and facilitate equal access by mitigating the potential negative effects of co-management policy and informing its future implementation.