Examining the ecological complexities of blackfoot paua demography and habitat requirements in the scope of marine reserve protection

<p>A critical question for ecologists and fisheries managers is what drives the demographic processes that dictate the abundance and size structure of ecologically and commercially important species. Marine Reserves (MRs) provide an opportunity to examine species in the absence of human disturbance (i.e. no fishing) and to investigate how habitat type, quantity and condition contribute to yield large individuals and dense aggregations that are typical of a more natural state. However, an improved understanding of the efficacy of marine reserves requires a robust examination of habitats inside and outside reserves to distinguish any reserve effect from a potential confounding habitat effect. Abalone are a valuable nearshore fishery in many parts of the world and many stocks have been overexploited to the point of collapse. Countries striving to rebuild their abalone stocks are utilizing MRs to support viable populations and focusing on habitat requirements that produce large aggregations and individuals. The abalone commonly referred to as the blackfoot paua (Haliotis iris) is a culturally and ecologically important New Zealand (NZ) species and is the focus of customary, recreational and commercial fisheries. However, the demography and growth rates of paua populations are highly variable, with pockets of “stunted” populations occurring throughout NZ. Density-dependent processes, differential juvenile success, variable habitat quality and fishing pressure have all been suggested to influence the fitness of individuals and the demography of paua populations. My research utilizes MRs to control for fishing activity and thereby to investigate ecological patterns and the effects of habitat on paua abundance and size variability. The main objectives of this thesis were to quantify the response of paua to MR status, distinguish habitat effect from a reserve effect and understand the contribution of habitat variables on demography and growth. Research was conducted within and surrounding five MRs in central NZ. The habitats in and outside MRs were not significantly different in physical and biogenic characteristics, but paua occurred in significantly greater densities and were significantly larger within four MRs compared with outside, illustrating that marine reserves do afford protection for paua. Paua within MRs were significantly more dense and larger in areas of relatively higher wave exposure and dense macroalgal cover. Despite protection, paua were found to be undersized or “stunted” at Long Island and Horoirangi MRs. I conducted surveys to evaluate the effect of density and the contribution of habitat variables on paua size at two spatial scales across environmental gradients. To further test the hypothesis that habitat effects growth a 12 month translocation experiment was conducted at Long Island MR. The surveys revealed that environmental gradients exist at small and large scales and explained how paua size varied along these gradients. The habitat variables which supported larger size individuals were consistent across both locations, where paua were significantly larger in areas that were exposed with high algal cover than those at sheltered areas with low algal cover. This result was further confirmed by the translocation experiment which revealed that paua translocated from a stunted environment to a normal environment grew significantly more than conspecifics placed at the stunted environment. To further explore the response of paua to protection and see if patterns were consistent across bioregions in areas with “normal” size paua I conducted research at the Taputeranga MR on the Wellington South Coast to evaluate juvenile and adult population densities and examine stage-specific habitat requirements. Juvenile paua were found in higher densities at fished sites in areas that were sheltered from wave exposure and dominated by cobbles and boulder fields. Adult paua were found in greater densities and were larger in size within the reserve than outside, which was the opposite finding to the baseline survey illustrating reserve effectiveness. Although within the reserve there were large aggregations and individual adults which may support population reproductive success, juvenile and adult population densities were not correlated. Results from this study indicate that marine reserve implementation does have an impact on adult populations but that habitat is more important for juvenile success. Although this thesis focused on paua within the scope of protection, MRs are placed in NZ to protect a suite of species. To thoroughly investigate habitats I conducted a rigorous inside-outside habitat analysis utilizing multibeam bathymetric data and video footage from drop camera surveys at Taputeranga MR. Habitat maps produced by NIWA were utilized to plan drop camera sampling locations and 278 drops were conducted across 8 sites associated with TMR. Analysis revealed that habitats within fished and reserve sites were comparable in physical and biogenic habitat quantities, although the reserve had greater topographic relief. However, when examining only a subsample of fished sites there were pronounced habitat differences between in and outside the reserve, where the western fished sites have significantly more rocky reef with greater algal cover than the reserve and eastern sites. These results illustrate the need for quantification of habitat when siting fished (control) areas and conducting inside versus outside reserve comparisons. This research has determined that MRs do afford protection for paua in central NZ. The differentiation between habitat and reserve effects that I have identified has direct relevance to current and future MRs in NZ and highlights the need for studies to examine habitat effect in MR spatial planning at a global level. Furthermore, this research highlights the importance of considering stage-specific habitat requirements when designing the spatial arrangement of MRs by protecting juvenile habitat as well as adults to increase chances of recovery. These abalone-habitat associations, showing the importance of exposure and macroalgal cover for growth, can be used to assist in management decisions within NZ such as considerations for siting management areas and potential translocations and are directly applicable to abalone conservation, management concerns and recovery efforts across the world.</p>

Examining the ecological complexities of blackfoot paua demography and habitat requirements in the scope of marine reserve protection

<p>A critical question for ecologists and fisheries managers is what drives the demographic processes that dictate the abundance and size structure of ecologically and commercially important species. Marine Reserves (MRs) provide an opportunity to examine species in the absence of human disturbance (i.e. no fishing) and to investigate how habitat type, quantity and condition contribute to yield large individuals and dense aggregations that are typical of a more natural state. However, an improved understanding of the efficacy of marine reserves requires a robust examination of habitats inside and outside reserves to distinguish any reserve effect from a potential confounding habitat effect. Abalone are a valuable nearshore fishery in many parts of the world and many stocks have been overexploited to the point of collapse. Countries striving to rebuild their abalone stocks are utilizing MRs to support viable populations and focusing on habitat requirements that produce large aggregations and individuals. The abalone commonly referred to as the blackfoot paua (Haliotis iris) is a culturally and ecologically important New Zealand (NZ) species and is the focus of customary, recreational and commercial fisheries. However, the demography and growth rates of paua populations are highly variable, with pockets of “stunted” populations occurring throughout NZ. Density-dependent processes, differential juvenile success, variable habitat quality and fishing pressure have all been suggested to influence the fitness of individuals and the demography of paua populations. My research utilizes MRs to control for fishing activity and thereby to investigate ecological patterns and the effects of habitat on paua abundance and size variability. The main objectives of this thesis were to quantify the response of paua to MR status, distinguish habitat effect from a reserve effect and understand the contribution of habitat variables on demography and growth. Research was conducted within and surrounding five MRs in central NZ. The habitats in and outside MRs were not significantly different in physical and biogenic characteristics, but paua occurred in significantly greater densities and were significantly larger within four MRs compared with outside, illustrating that marine reserves do afford protection for paua. Paua within MRs were significantly more dense and larger in areas of relatively higher wave exposure and dense macroalgal cover. Despite protection, paua were found to be undersized or “stunted” at Long Island and Horoirangi MRs. I conducted surveys to evaluate the effect of density and the contribution of habitat variables on paua size at two spatial scales across environmental gradients. To further test the hypothesis that habitat effects growth a 12 month translocation experiment was conducted at Long Island MR. The surveys revealed that environmental gradients exist at small and large scales and explained how paua size varied along these gradients. The habitat variables which supported larger size individuals were consistent across both locations, where paua were significantly larger in areas that were exposed with high algal cover than those at sheltered areas with low algal cover. This result was further confirmed by the translocation experiment which revealed that paua translocated from a stunted environment to a normal environment grew significantly more than conspecifics placed at the stunted environment. To further explore the response of paua to protection and see if patterns were consistent across bioregions in areas with “normal” size paua I conducted research at the Taputeranga MR on the Wellington South Coast to evaluate juvenile and adult population densities and examine stage-specific habitat requirements. Juvenile paua were found in higher densities at fished sites in areas that were sheltered from wave exposure and dominated by cobbles and boulder fields. Adult paua were found in greater densities and were larger in size within the reserve than outside, which was the opposite finding to the baseline survey illustrating reserve effectiveness. Although within the reserve there were large aggregations and individual adults which may support population reproductive success, juvenile and adult population densities were not correlated. Results from this study indicate that marine reserve implementation does have an impact on adult populations but that habitat is more important for juvenile success. Although this thesis focused on paua within the scope of protection, MRs are placed in NZ to protect a suite of species. To thoroughly investigate habitats I conducted a rigorous inside-outside habitat analysis utilizing multibeam bathymetric data and video footage from drop camera surveys at Taputeranga MR. Habitat maps produced by NIWA were utilized to plan drop camera sampling locations and 278 drops were conducted across 8 sites associated with TMR. Analysis revealed that habitats within fished and reserve sites were comparable in physical and biogenic habitat quantities, although the reserve had greater topographic relief. However, when examining only a subsample of fished sites there were pronounced habitat differences between in and outside the reserve, where the western fished sites have significantly more rocky reef with greater algal cover than the reserve and eastern sites. These results illustrate the need for quantification of habitat when siting fished (control) areas and conducting inside versus outside reserve comparisons. This research has determined that MRs do afford protection for paua in central NZ. The differentiation between habitat and reserve effects that I have identified has direct relevance to current and future MRs in NZ and highlights the need for studies to examine habitat effect in MR spatial planning at a global level. Furthermore, this research highlights the importance of considering stage-specific habitat requirements when designing the spatial arrangement of MRs by protecting juvenile habitat as well as adults to increase chances of recovery. These abalone-habitat associations, showing the importance of exposure and macroalgal cover for growth, can be used to assist in management decisions within NZ such as considerations for siting management areas and potential translocations and are directly applicable to abalone conservation, management concerns and recovery efforts across the world.</p>

A seascape approach for guiding effective habitat enhancement

Kelp habitats are threatened across the globe, and because of their ecological importance, active conservation and restoration solutions are needed. The use of man-made structures as artificial reefs is one way to enhance kelp habitat by providing suitable substrata, but in the past the ecology of artificial structures has been investigated mainly in contrast to natural coastal habitats, not as elements integrated into the seascape. Indeed, it is now emerging that structuring processes, including ecological interactions (e.g., herbivory), can depend on properties of the surrounding seascape. In Eastern Canada, grazing by the green sea urchin can jeopardize the success of artificial reefs for kelp enhancement. Urchin activity is, however, likely to be influenced by the bottom composition, and thus a seascape approach is needed to integrate urchin behavior and habitat heterogeneity. Adopting a spatially explicit framework, we investigated whether the seascape creates areas of differential grazing risk for kelp by affecting urchin habitat use. Specifically, we transplanted kelp onto modules of artificial substrata distributed on a heterogeneous area that we mapped for bottom type and algal cover. After following kelp survival and urchin distribution over time, we modeled kelp survival as function of urchin metrics and coupled it to urchin use of the habitat models to map grazing risk in the area. Kelp survival was a function of the frequency of the urchins presence. Urchins avoided sandy patches, while bottom composition and algal cover modulated the within-patch urchin use of the habitat, creating heterogeneity in grazing risk. Discrete seascape features (boulders) also increased the grazing risk locally. The heterogeneity of coastal seafloor can thus play a major role in determining the ecological outcomes on artificial structures. Incorporating this information when planning artificial reefs could minimize the detrimental grazing risk, thereby increasing the success of artificial reefs for kelp habitat enhancement.

Ecological and environmental context shape the differential effects of a facilitator in its native and invaded ranges

Non-indigenous species often exhibit disproportionately strong negative effects in their introduced range compared to their native range, and much research has been devoted to understanding the role of shared evolutionary history, or lack thereof, in driving these differences. Less studied is whether non-indigenous species, particularly those that are important as facilitators in their native range, have persistent positive effects in their invaded range despite a lack of a shared evolutionary history with the invaded community. Here, we manipulated the density of a habitat-forming facilitator, the high intertidal acorn barnacle Balanus glandula, factorially with herbivore density in its native range (Bluestone Point, British Columbia, Canada) and invaded range (Punta Ameghino, Chubut Province, Argentina) to determine how this facilitator differentially affects associated species at these two locations. Given that high intertidal species at Punta Ameghino (PA) are evolutionarily naïve to barnacles, we predicted that the positive effects of B. glandula at PA would absent or weak compared to those at Bluestone Point (BP). However, we found that B. glandula had an equally positive effect on herbivore biomass at PA compared to BP, possibly because the moisture-retaining properties of barnacle bed habitats are particularly important in seasonally dry Patagonia. Barnacle presence indirectly decreased ephemeral algal cover at BP by increasing grazer pressure, but barnacles instead facilitated ephemeral algae at PA. In contrast, B. glandula increased perennial algal cover at BP, but generally decreased perennial algal cover at PA, likely due to differences in dominant algal morphology. These results suggest that shared evolutionary history is not a prerequisite for strong facilitation to occur, but rather that the nature and strength of novel species interactions are determined by the traits of associated species and the environment in which they occur.

Welcome to the jungle: Algal turf negatively affects recruitment of a Caribbean octocoral

ABSTRACTAlgal cover has increased and scleractinian coral cover has steadily declined over the past 40 years on Caribbean coral reefs. In contrast, octocoral abundance has increased at those sites where octocoral abundances have been monitored. The effects of algal cover on recruitment may be a key component in these patterns, as upright octocoral recruits have the potential to escape competition with algae by growing above the ubiquitous algal turfs. However, the impacts of algal turf on octocorals have not been tested.We used laboratory and field recruitment experiments to examine impacts of algal turf on settlement and then survival of newly-settled octocorals. Tiles were preconditioned on a Caribbean reef, allowing algae to settle and grow. Tiles were then partitioned into three treatments: lightly scrubbed (0% turf cover), left alone (19% turf cover), or kept for 15 days in a sea table without fish or large invertebrate herbivores (50% turf cover). Planulae of the common Caribbean octocoral Plexaura homomalla were allowed to settle and metamorphose on the tiles for six days. Tiles were then deployed onto a reef and survival of those recruits was monitored for seven weeks. Settlers that recruited to the tiles after deployment to the reef were also monitored.Laboratory recruitment rate was significantly higher in lower turf cover treatments. Field survival was significantly reduced by increased turf cover; for every 1% increase in turf cover, polyps died 1.3% faster. In a model parameterized by the observed field survival, polyps exposed to 100% turf cover had a 2% survival rate over 51 days, while polyps exposed to no turf cover had a 32% survival rate over the same time.Synthesis. We found that high densities of turf algae can significantly inhibit recruitment of octocorals. Octocoral survival rates were similar to those published for scleractinians, but field settlement rates were much higher, which likely contributes to the higher resilience of octocorals to disturbances. The factors that influence recruitment are critical in understanding the dynamics of octocorals on Caribbean reefs as continuing declines in scleractinian cover may lead to more octocoral-dominated communities in the Caribbean.

Reducción en la cobertura coralina del arrecife de La Chola (Pacífico Oriental Tropical)

La Chola Reef is located at the easternmost sector of the Eastern Tropical Pacific. This coral formation of 11 ha is dominated by branching corals of the genus Pocillopora. The main goal of this study was to evaluate changes in coral cover over time, by comparing data collected in 2002 and 2013, implementing the chain transect methodology. Additionally, we generated an up-to-date map of this reef using field data collected with a GPS and present the first in-situ water temperature data. The reef exhibited a 20% coral cover decline during the study period, with associated increases in algal cover (mainly coralline algae). Total extension of the reef seems to have remained stable during the last 30 years. Besides the usual stressors commonly associated with limitations in coral reef development in this region of the Pacific, seasonal decreases in temperature are proposed as a potential cause of coral cover loss on the deeper sectorsof the reef.

Temporal dynamics of coral and algal cover and their potential drivers on a coral reef of Gorgona Island, Colombia (Eastern Tropical Pacific)

Los arrecifes coralinos son ecosistemas altamente dinámicos, a menudo afectados por diversas perturbaciones naturales. Sin embargo, descensos dramáticos en la cobertura coralina durante décadas recientes llevan a preguntar si tales descensos han sido causados por crecientes impactos antropogénicos. Con este fin, la dinámica de la cobertura de coral y algas se estudió a partir de datos recolectados entre 1998-2014 de 20 transectos fijos de 10 m a dos profundidades en dos sitios de La Azufrada, un arrecife coralino libre de impactos humanos locales, situado en Isla Gorgona, Colombia. La cobertura coralina disminuyó de 66,9 % en 1998 a 39,4 % en 2008, pero luego aumentó a 50,7 % en 2014. La cobertura de algas carnosas y de césped fue baja entre 1998-2004, aumentó a 49,5 % en 2007 y luego disminuyó a < 33,0 %. Las algas coralinas incrustantes fueron las más escasas hasta 2009, cuando aumentaron al disminuir las algas carnosas y de césped. La variación temporal fue diferente entre profundidades con las áreas someras exhibiendo los mayores descensos en la cobertura coralina hasta 2008, pero una recuperación significativa desde entonces. En contraste, la cobertura coralina en áreas profundas disminuyó sólo ligeramente. La exposición subaérea prolongada de los corales durante mareas bajas extremas parece impulsar un ciclo de perturbación y recuperación de los corales. El crecimiento de los corales hace que el arrecife sea más propenso a la exposición subaérea, después de lo cual los corales se blanquean, mueren y son colonizados por algas filamentosas y carnosas. Los erizos de mar y los peces herbívoros aumentan su abundancia en respuesta al aumento de la cobertura de algas y controlan el crecimiento de algas, dejando el sustrato cubierto por algas coralinas incrustantes que lo adecúan para el asentamiento de larvas de coral producidas sexualmente. La fragmentación por agentes físicos y biológicos (como los coralívoros) incrementa el reclutamiento de coral y el arrecife entra en una fase de recuperación coralina. Aunque este arrecife es resiliente a la exposición subaérea porque está protegido de perturbaciones antropogénicas, las crecientes amenazas del cambio climático global pueden comprometer su futura resiliencia. © 2017. Acad. Colomb. Cienc. Ex. Fis. Nat.

"Caracterización ficoflorística de los paredones de la Sierra de Juárez, Oaxaca. Importancia de las formas de crecimiento algales en la tipificación de un ambiente."

This study shows the importance of integrating the physiography of a cummunity with the visible manifestation of algae, that we call growth form, to characterize communities in terms of the growth forms that typify it. The drip walls of Sierra de Juarez were analyzed with this approach. The growth forms present are: compact hemispherical growths, filamentous flocculus, mucilaginous flocculus, compact films filamentous films, rugs and crusts. These forms are described from 15 samples. 53.3% of the flocculus type, 33.3% of these are filamentous and 20% are mucilaginosus. Our descriptions of the algal cover and physiography of the Sierra de Juarez are very similar to the descriptions of drip walls in other latitudes, also with a predominance of flocculus growths. We define a drip wall as a vertical wall with not very much water and filamentous and mucilaginous flocculus as typical growth forms.

A survey of the seaweeds of Lennox Passage and St. Peters Bay, Cape Breton Island, Nova Scotia

A novel, bay-scale (i.e. tens of km) survey method was employed to examine algal populations on the southwestern shore of Cape Breton Island, Nova Scotia. Since traditional remote sensing methods were unlikely to be successful in these waters, underwater video and acoustic methods were applied. A transponder positioned towfish housing video camera and sidescan sonar was hauled along predetermined transects perpendicular to shore to provide information on bottom type and algal cover. The towfish data were used to ground truth echosounder data (bottom type and macrophyte canopy height) collected along 5, 10 and 20 m depth contour lines. The survey area was divided into six zones comprising a range of exposure, depth and bottom types. Destructive quadrat samples were collected at each depth, plus shore stations, to provide biomass estimates. Over thirty taxa were enumerated, indicating depths and zones of common occurrence. Ascophyllum was abundant at some of the shore stations. The genera Chondrus, Cystoclonium, Desmarestia, Fucus, Phyllophora, Polysiphonia, and Saccharina were common at 5 m. Desmarestia and Saccharina dominated at 10 m with wet weights sometimes over 1 kg·m-2. Agarum dominated at 20 m. The towfish / echosounder grid sampling system was relatively coarse in order to cover the 140 km2 survey area within 12 days. As a result, the survey did not produce spatially detailed information. However, adequate information was gathered to describe the general characteristics of bottom type and algal cover by zone and for focussing further exploration.