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Study sites around Cape Arago (A) and Port Orford (B), Oregon. Sampled transects are indicated by the long lines with arrows at both ends.
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Foam lines oriented parallel to shore are common features of rocky shores. At times, the water coloration is different on either side of the foam lines, suggesting they are associated with fronts. We investigated the effect of shore-parallel foam lines and associated fronts on distributions of holo- and meroplankton. We performed CTD transects to d...
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... data and zooplankton samples were collected along transects through Sunset Bay, Cape Arago, Oregon (43 20.13 0 N, 124 22.40 0 W; Figure 1A) during the summers of 1997 (18 and 25 July, 1 August), 1999 (25 June, 20 July and 8 September) and 2000 (19 and 21 July, 16 and 24 August). In 2000, we also sampled transects at Shore Acres and Miller's Cove, Cape Arago, Oregon (43 19.5 0 N, 124 23.5 0 W and 43 20.25 0 N, 124 22.5 0 W, respectively; Figure 1A) and Nellies Cove, Port Orford, Oregon (42 44.75 0 N, 124 29.75W; Figure 1B). ...
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... data and zooplankton samples were collected along transects through Sunset Bay, Cape Arago, Oregon (43 20.13 0 N, 124 22.40 0 W; Figure 1A) during the summers of 1997 (18 and 25 July, 1 August), 1999 (25 June, 20 July and 8 September) and 2000 (19 and 21 July, 16 and 24 August). In 2000, we also sampled transects at Shore Acres and Miller's Cove, Cape Arago, Oregon (43 19.5 0 N, 124 23.5 0 W and 43 20.25 0 N, 124 22.5 0 W, respectively; Figure 1A) and Nellies Cove, Port Orford, Oregon (42 44.75 0 N, 124 29.75W; Figure 1B). ...
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... data and zooplankton samples were collected along transects through Sunset Bay, Cape Arago, Oregon (43 20.13 0 N, 124 22.40 0 W; Figure 1A) during the summers of 1997 (18 and 25 July, 1 August), 1999 (25 June, 20 July and 8 September) and 2000 (19 and 21 July, 16 and 24 August). In 2000, we also sampled transects at Shore Acres and Miller's Cove, Cape Arago, Oregon (43 19.5 0 N, 124 23.5 0 W and 43 20.25 0 N, 124 22.5 0 W, respectively; Figure 1A) and Nellies Cove, Port Orford, Oregon (42 44.75 0 N, 124 29.75W; Figure 1B). ...
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... were made roughly every other day, starting in January 2000 and continuing through September. Observations of Miller's Cove and Sunset Bay were made from an overlook just south of the entrance to Sunset Bay State Park (Figure 2A, #1). Observations of Shore Acres and Simpson Reef were made from the Simpson Reef overlook parking area (Figure 2A, #2). ...
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... description A crescent-shaped beach and stream are at the head of Sunset Bay, a small bay on the southern Oregon coast ( Figures 1A and 2A). About 300 m from shore, the bay becomes tightly constricted, then opens up to form the outer portion of the bay. ...
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... shore-parallel foam line or, frequently, a pair of parallel foam lines extends from the rock reef on the north side of the bay to the reef to the south ( Figure 1A). The foam line is generally connected $25 m landward of the most seaward rocks. ...
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... of the foam lines, at $0.6 km from shore, subsurface isotherms were domed upward, and landward of this dome they bent steeply downward so that the thermocline (centered around the 9.0 C isotherm) contacted the bottom at $0.1 km from shore. Surface Chl concentrations were higher seaward of the foam line than landward, with lowest values found immediately adjacent to shore (Figure 10). High concen- trations of Chl were found just below the thermocline where it was bent downward toward the bottom. ...
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... samples were collected at each CTD station. The cluster analysis suggested that there were two patterns of distribution ( Figure 11): organisms with highest concentrations seaward of the inner foam line and front (i.e. seaward of 0.2 km); and those with their highest concentrations landward of the inner foam line (i.e. ...
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... former group of organ- isms, adult and nauplii calanoid copepods, barnacle nauplii stages 4, 5 and 6, zoeae, polychaete larvae with three or fewer setigers and polychaete larvae with more than three setigers, were significantly more concentrated seaward of the front (Table II). Barnacle cyprids, phor- onid larvae, gastropod veligers, mussel larvae, and planula, were found at higher, but not significantly higher, concentrations seaward of this front ( Figure 10; Table II). In contrast, harpacticoid copepods and Littorina egg cases were most abundant at the stations landward of the inner foam line. ...
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... Shore Acres transect was located $0.5 km south of Sunset Bay and $300 m north of the Shore Acres State Park wave viewing kiosk (Figure 1). The shoreline from Sunset Bay south for 3 km is oriented roughly toward the NW and composed of rocky reefs and cliffs (Figure 2). ...
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... the shore, the thermocline isotherms tilted upward toward the surface. On 19 July, this occurred within 100 m of shore, and the thermocline did not contact the surface (Figure 12). A foam line was located $200 m from shore. ...
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... thermal front and associated foam line were located $0.4 km from shore, where the thermocline (9.9 C iso- therm) contacted the surface. Landward of this front, surface waters were cooler and denser than on the sea- ward side, and isotherms cooler than 9.8 C were bent downward (Figures 12 and 13). The lowest concentrations of Chl were found in the waters within several hundred meters of shore and extended throughout the water column ( Figure 12). ...
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... of this front, surface waters were cooler and denser than on the sea- ward side, and isotherms cooler than 9.8 C were bent downward (Figures 12 and 13). The lowest concentrations of Chl were found in the waters within several hundred meters of shore and extended throughout the water column ( Figure 12). Higher Chl concentrations were within or below the thermocline, and just seaward of these waters with the lowest Chl concentrations. ...
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... Chl concentrations were within or below the thermocline, and just seaward of these waters with the lowest Chl concentrations. On 16 August, the highest Chl concen- trations were beneath the front where the thermocline intercepted the surface (Figure 12). Distributions of oceanographic parameters at Sunset Bay on 19 July and 16 August (Figures 3 and 4) were quite different from those observed at Shore Acres (Figure 12). ...
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... 16 August, the highest Chl concen- trations were beneath the front where the thermocline intercepted the surface (Figure 12). Distributions of oceanographic parameters at Sunset Bay on 19 July and 16 August (Figures 3 and 4) were quite different from those observed at Shore Acres (Figure 12). At Sunset Bay on 19 July, there was a lens of warm water adjacent to shore, and at the bay mouth isotherms were bent downward. ...
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... Sunset Bay on 19 July, there was a lens of warm water adjacent to shore, and at the bay mouth isotherms were bent downward. No lens of warm water was observed off Shore Acres and isotherms tilted upward as shore was approached (Figure 12). At Sunset Bay on 16 August, there was also a lens of warm water adjacent to shore and isotherms within the thermocline (9.9-9.0 ...
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... zooplankton data from 19 July and 16 August 2000 are presented in Figures 13 and 14. Data from the longer transect sampled on 17 August were analyzed statistic- ally and this analysis suggests there were two general patterns of zooplankton distribution (Figure 15). ...
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... zooplankton data from 19 July and 16 August 2000 are presented in Figures 13 and 14. Data from the longer transect sampled on 17 August were analyzed statistic- ally and this analysis suggests there were two general patterns of zooplankton distribution (Figure 15). The first pattern was typified by the distribution of calanoid copepods and their nauplii. ...
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... first pattern was typified by the distribution of calanoid copepods and their nauplii. Concentrations were rela- tively high at the most seaward stations, peaked at the station on the seaward side of the thermal front ( Figure 13A, 0.7 km), and then fell to low concentrations at stations landward of the thermal front, with lowest concentrations at the station adjacent to shore. Note, however, that concentrations varied by only about a factor of four over the entire transect. ...
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... however, that concentrations varied by only about a factor of four over the entire transect. Organisms with similar distributions to calanoid copepods included gastropod veligers, mussel larvae, nudibranch veligers, zoeae and Littorina veligers (Figure 16) 1 10 20 30 40 50 60 70 80 90 Figure 12. a Larvae that were significantly more abundant landward and seaward of the front and foam line are indicated by -and + signs, respectively. ...
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... however, that concentrations varied by only about a factor of four over the entire transect. Organisms with similar distributions to calanoid copepods included gastropod veligers, mussel larvae, nudibranch veligers, zoeae and Littorina veligers (Figure 16) 1 10 20 30 40 50 60 70 80 90 Figure 12. a Larvae that were significantly more abundant landward and seaward of the front and foam line are indicated by -and + signs, respectively. ...
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... more concentrated seaward of the front (Table III). The second pattern of zooplankton distribution can be typified by the distribution of polychaete larvae with three or fewer setigers ( Figure 13E). Seaward of the thermal front, concentrations were very low, increased rapidly landward of the front and then fell sharply (by a factor of $10) within 200 m of shore. ...
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... of zooplankton along the shorter tran- sect sampled on 19 July 2000 appear similar to those within 500 m of shore on 16 August (Figures 13 and 15). On both dates, relatively high concentrations of cope- pods and copepod nauplii were found within 100 m of shore. ...
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... difference in zooplankton distributions at Sunset Bay ( Figures 5 and 7) and Shore Acres (Figures 13 and 14) are most clearly demonstrated with the distribution of calanoid copepods. At Sunset Bay, calanoid copepods were significantly more abundant seaward of the front, and their numbers fell by at least an order of magnitude across the front. ...
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... Cove is located $0.5 km from the breakwater at Port Orford, Oregon (Figure 1) and $12 km south of Cape Blanco, a major upwelling center. At Port Orford, a headland (altitude $100 m) juts out into the ocean, forming a bight to the south that is sheltered from the north winds (Figure 1). ...
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... Cove is located $0.5 km from the breakwater at Port Orford, Oregon (Figure 1) and $12 km south of Cape Blanco, a major upwelling center. At Port Orford, a headland (altitude $100 m) juts out into the ocean, forming a bight to the south that is sheltered from the north winds (Figure 1). Nellies Cove is composed of two narrow (<100 m wide) coves surrounded by high cliffs (Figure 1). ...
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... Port Orford, a headland (altitude $100 m) juts out into the ocean, forming a bight to the south that is sheltered from the north winds (Figure 1). Nellies Cove is composed of two narrow (<100 m wide) coves surrounded by high cliffs (Figure 1). Transects began <30 m from the cobble beach at the head of the western arm of Nellies Cove and ran along the long axis of the cove, and out to sea. ...
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... associated with this foam line: bay waters were milky in appearance, while those offshore were clear. Warmest waters were located inside Nellies Cove and landward of the foam line ( Figure 16). The fluorometer failed on 17 August. ...
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... fluorometer failed on 17 August. On 31 August, Chl concentrations were highest below the foam line and front at the cove mouth ( Figure 16); concentrations were up to seven times higher than to either side of the front. The foam line delineated a front in water coloration and temperature. ...
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... 0.5 (17 August) and 1.1 km (31 August) from shore we observed a second surface thermal front (Figure 16). At 1-1.5 km from shore, seaward of the shelter of the Port Orford Bight, the mixed layer deepened and iso- therms below 15 or 20 m tilted downward (Figure 16). ...
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... 0.5 (17 August) and 1.1 km (31 August) from shore we observed a second surface thermal front (Figure 16). At 1-1.5 km from shore, seaward of the shelter of the Port Orford Bight, the mixed layer deepened and iso- therms below 15 or 20 m tilted downward (Figure 16). ...
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... 17 August 2000, there were two patterns of zoo- plankton distribution (Figure 17). Most organisms were more abundant seaward of the foam line at the cove mouth ( Figure 18). ...
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... 17 August 2000, there were two patterns of zoo- plankton distribution (Figure 17). Most organisms were more abundant seaward of the foam line at the cove mouth ( Figure 18). For example, calanoid copepods were at concentrations around 10 4 m À3 seaward of the foam line, but concentrations fell to 10 2 m À3 inside the cove. ...
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... cluster analysis identified a second group of organisms most concentrated around the foam line at the cove mouth ( Figure 17). The distributions of harpac- ticoid copepods and their nauplii were particularly striking (Figure 18). ...
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... cluster analysis identified a second group of organisms most concentrated around the foam line at the cove mouth ( Figure 17). The distributions of harpac- ticoid copepods and their nauplii were particularly striking (Figure 18). At the two stations centered on the foam line, harpacticoid nauplii were at concentrations between 10 4 and nearly 10 5 m À3 , but just tens of meters away, at adjacent stations, their numbers fell to near zero. ...
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... oceanography of Port Orford Bight appears to be complex. We observed a front at the mouth of Nellies Cove and additional fronts at $0.5 and 1-1.2 km from shore ( Figure 18). The geographic setting of Port Orford Bay is quite similar to the north side of Monterey Bay, California, where Graham and co-workers also found a lens of warm water on the lee side of a bay for an upwelling-favorable wind ( Graham et al., 1992;Graham, 1993;Graham and Largier, 1997). ...
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Citations
... A large body of literature on a variety of fronts has demonstrated that these features influence the abundance and distribution of organisms. Franks (1992) presented a simple model showing how density-driven fronts can aggregate plankton through interactions between frontal flow regimes and the variable swimming abilities and behaviors of different planktonsubsequently observed by Shanks et al. (2003), Weidberg et al. (2014), and others. Buoyant or upward swimming plankton converge on the stratified side of a density-driven front, and the tightness of the aggregation depends on the strength of upward motion. ...
... At the same time, the front acts as a barrier to cross-frontal mixing of plankton (Woodson et al., 2012). Density-driven fronts can accumulate planktonic organisms from either side as they are drawn towards the front by secondary flow structures (Franks, 1992;Shanks et al., 2003;Bjorkstedt et al., 2002;Karati et al., 2018). Shear-driven fronts (e.g., flow separations) can also create planktonic spatial structure by bringing two water masses into close proximity, yielding high gradients, or by injecting one water mass between two others (i.e., an intrusion). ...
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... The physical processes and biological mechanisms driving coastal larval transport have been extensively studied, and yet remain poorly understood in the nearshore (here defined as within 1 km from shore but excluding the surfzone; reviewed in . This is partly because studies on intertidal species suggest that larval transport and dispersal can be episodic, and occur at smaller spatial scales than previously anticipated, with larvae often remaining within the nearshore close to settlement sites (Shanks et al., 2003;Tapia and Pineda, 2007;Morgan et al., 2009;Shanks and Shearman, 2009;Hagerty et al., 2018). The generally poor horizontal swimming capabilities of larvae (Chia et al., 1984) make them susceptible to being swept away due to the advective nature of the nearshore (Lentz and Fewings, 2012). ...
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... During this study, each frontal event was characterised by different hydrological and physical conditions. Surface slicks are associated with one or a combination of wind-driven, buoyancy, topographic or tidally generated physical forcing mechanisms and are often interpreted as propagating features associated with internal waves (Franks, 1992a;Leichter et al., 1998;McCulloch and Shanks, 2003;Shanks et al., 2003). Previous research within the same study region suggested that these fronts are formed by internal waves (Weidberg et al., 2019) and appeared to follow the predictions of Pineda's (1994) two-phase model for cross-shore internal tidal bores. ...
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... pH 8. 06-8.07 in open ocean site California Current Ecosystem off Santa Barbara, Hofmann et al., 2011). Alternatively, larvae could be retained by small and meso-scale oceanographic features, such as the coastal boundary layer, eddies, internal tides, or topographically-generated fronts, so that they are maintained in variable nearshore conditions for their entire larval life (Shanks et al., 2003;Nickols et al., 2015;Liévana MacTavish et al., 2016;Shulzitski et al., 2016). In addition to horizontal transport, changes in vertical distribution can also affect the physical conditions that larvae experience (Metaxas and Saunders, 2009). ...
Many marine organisms have a multi-phase life history and rely on their planktonic larvae for dispersal. Despite the important role of larvae in shaping population distribution and abundance, the chemical, physical, and biological factors that shape larval fate are still not fully understood. Shedding light into this larval dispersal “black box” has become critical in the face of global climate change, primarily due to the importance of larval dispersal in formulating sound conservation and management strategies. Focusing on two major stressors, warming and acidification, we highlight the limitations of the current species-by-species, lab-based study approach, and particularly the lack of consideration of the larval experience along the dispersive pathway. Measuring organismal responses to environmentally relevant climate change stress demands an improved documentation of the physical and biological conditions that larvae experience through ontogeny, which in turn requires updated empirical and theoretical approaches. While there are meaningful between taxa comparisons to be made by larval ecologists, to peek into the dispersal black box and to investigate the larger scale consequences of altered dispersal requires innovative collaborations between ecologists, oceanographers, molecular biologists, statisticians, and mathematicians.
... the downward vertical flow which characterizes these convergent structures (Franks 1992;Pineda 1999;Shanks et al. 2000;Weidberg et al. 2014). Fronts can be formed by multiple hydrographical processes operating at different spatiotemporal scales including Ekman forcing, estuarine circulation, tides, and topographically driven currents (Le Fevre 1986;Shanks et al. 2003). Processes that cause accumulation at these fronts, like internal waves and upwelling, may become crucial for benthic larval aggregation. ...
Vertical migrations of zooplankters have been widely described, but their active movements through shallow, highly dynamic water columns within the inner shelf may be more complex and difficult to characterize. In this study, invertebrate larvae, currents, and hydrographic variables were sampled at different depths during and after the presence of fronts on three different cruises off the southern coast of South Africa. Internal wave dynamics were observed in the hydrographic data set but also through satellite imagery, although strong surface convergent currents were absent and thermal stratification was weak. During the first two cruises, fronts were more conspicuous and they preceded strong onshore currents at depth which developed with the rising tide. Vertical distributions of larvae changed accordingly, with higher abundances at these deep layers once the front disappeared. The third cruise was carried out during slack tides, the front was not conspicuous, deep strong onshore currents did not occur afterward and larval distributions did not change consistently through time. Overall, the vertical distributions of many larval taxa matched the vertical profiles of shoreward currents and multivariate analyses revealed that these flows structured the larval community, which was neither influenced by temperature nor chlorophyll. Thus, the ability to regulate active vertical positioning may enhance shoreward advection and determine nearshore larval distributions.
... These and many other processes often interact together in determining recruitment variation at multiple spatial and temporal scales (see Pineda et al. 2007Pineda et al. , 2009). For instance, the spatial variation detected in P. candei recruitment likely reflects the intricate influence of several spatially structured nearshore processes operating at very localized spatial scales i.e. without ruling out stochastic events by themselves, features such as local geomorphology (Palma et al. 2006), substrate microtopography (Kohler et al. 1999) and local flow patterns (Archambault and Bourget 1999;Shanks et al. 2003) may interact in a complex way to determine if recruits are to occur ...
The uptake of natural living resources for human consumption has triggered serious changes in the balance of ecosystems. In the archipelagos of Macaronesia (NE Atlantic), limpets have been extensively exploited probably since islands were first colonized. This has led to profound consequences in the dynamics of rocky shore communities. The specific objectives of this thesis were to: 1) develop and characterize species-specific microsatellite markers for the limpets Patella candei (d’Orbigny 1840) and Patella aspera (Röding 1798), endemic to the Macaronesia archipelagos; 2) assess their genetic diversity, population structure and contemporary levels of connectivity throughout Macaronesia; 3) conduct a morphometric analysis of the P. candei complex to complement molecular data; 4) evaluate the temporal and spatial variation in recruitment of P. candei and study its association with real-time environmental data; 5) assess the effect of temperature on larval development of P. candei; and 6) provide general recommendations to foster the sustainable exploitation of limpets in Macaronesia. A total of twelve and seventeen microsatellite markers were described for P. candei and P. aspera, respectively. These showed clean polymorphisms and speciesspecific markers were combined in three optimized multiplex reactions. For P. candei, a highly significant genetic break between archipelagos following isolation by distance was detected. Contrastingly, significant genetic differentiation among islands (i.e. Azores) was absent possibly indicating ongoing gene flow via larval exchange between populations. Significant shell shape differences among archipelagos were also detected using both distance-based and geometric morphometric analyses. Adaptive processes associated with niche differentiation and strong barriers to gene flow among archipelagos may be the mechanisms underlying P. candei diversification in Macaronesia. As for P. aspera, genetic analyses showed significant population structure between populations from Azores and populations from Madeira and Canaries, and absence of current or historic gene flow between these. Results also suggest that both population clusters have experienced demographic changes over time. Heterozygote deficits were common across populations, which can be better accounted for by inbreeding than by null alleles or Wahlund effect. Such levels of inbreeding are likely a consequence of a significant reduction of reproductive units due to decades of intense exploitation. The monitoring program applied to track P. candei recruitment showed that early recruits occurred throughout the entire duration of the program, but its intensity varied in space and time. In general, a marked peak in recruitment occurred during winter/spring months, the period of greatest reproductive activity, when sea surface temperatures are lower and wave turbulence higher. Significant wave height was probably the most important proximate cue triggering the recruitment of P. candei, which eventually depends on adequate ultimate drivers for spawning and reproduction (i.e. temperature). Indeed, as a winter-breeder, P. candei larvae seem to perform better and attain higher fitness at colder temperatures. In fact, experimental treatments on larval rearing showed that larval development was faster at increasing temperatures but cumulative survivorship decreased; about 25% of larvae at higher temperatures survived to the end of the experiment, a 2-fold decrease from the average survivorship of ~ 50% at lower temperatures. Overall, the outcomes of this thesis fill a gap in our knowledge about processes involved in determining the connectivity patterns between limpet populations and the environmental factors influencing such patterns across the Macaronesia region. The present study is an important first step in this direction of using multi-faceted approaches to understand complex processes operating at the marine environment, while providing a fundamental asset to define stocks and thus inform specific conservation strategies that foster the sustainable exploitation of limpets throughout Macaronesia archipelagos.
... Larvae swim or migrate vertically to help regulate their retention or dispersal, either continuously or through diel or ontogenetic vertical migrations (Bradbury and Snelgrove, 2001;Epifanio and Cohen, 2016;Epifanio and Garvine, 2001;Morgan, in press;Queiroga and Blanton, 2005). Larvae can swim vertically to find favorable horizontal currents ( Paris and Cowen, 2004), or swim against vertical velocities to maintain their depth, often resulting in aggregations at fronts (Bjorkstedt et al., 2002;Franks, 1992;Graham et al., 1992;Ryan et al., 2014;Shanks et al., 2000;Shanks et al., 2003a) or the coast ( Genin et al., 2005;Shanks and Brink, 2005). Modeling studies show relatively small changes in depth Fig. 1. ...
... The shoreline was divided into 100 equally sized, 25 km 2 polygons, each extending 3.5 km offshore (Fig. 2) and acting as both a release and destination cell. As our model lacks the spatial resolution necessary to model many of the very nearshore ( Shanks et al., 2003a) processes affecting settlement, we measure nearshore larval supply, defined as the total number of larvae found within any destination cell anytime after 30 days of development. Each larva could only contribute to this quantity once for any given release scenario. ...
... Fronts are associated with phytoplankton blooms and aggregate phyto- plankton and larvae, and these phenomena are well-documented in central California ( Bjorkstedt et al., 2002;Graham et al., 1992;Ryan et al., 2010Ryan et al., , 2014Traganza and Conrad, 1981;Woodson et al., 2009). Fronts are common and persistent in the CCS ( Castelao et al., 2006;Shanks et al., 2003a), and are spatially correlated with higher recruit- ment of both intertidal and subtidal species ( Woodson et al., 2012). However, fronts may also inhibit recruitment locally by preventing larval-rich water from reaching shore ( Galarza et al., 2009;McCulloch and Shanks, 2003). ...
