3 research outputs found
Combining Distribution and Dispersal Models to Identify a Particularly Vulnerable Marine Ecosystem
Habitat suitability models are being used worldwide to help map and manage marine areas of conservation importance and scientific interest. With groundtruthing, these models may be found to successfully predict patches of occurrence, but whether all patches are part of a larger interbreeding metapopulation is much harder to assert. Here we use a North Atlantic deep-sea case study to demonstrate how dispersal models may help to complete the picture. Pheronema carpenteri is a deep-sea sponge that, in aggregation, forms a vulnerable marine ecosystem in the Atlantic Ocean. Published predictive distribution models from United Kingdom and Irish waters have now gained some support from targeted groundtruthing, but known aggregations are distantly fragmented with little predicted habitat available in-between. Dispersal models were used to provide spatial predictions of the potential connectivity between these patches. As little is known of P. carpenteri’s reproductive methods, twenty-four model set-ups with different dispersal assumptions were simulated to present a large range of potential dispersal patterns. The results suggest that up to 53.1% of the total predicted habitat may be reachable in one generation of dispersal from known populations. Yet, even in the most dispersive scenario, the known populations in the North (Hatton-Rockall Basin) and the South (Porcupine Sea Bight) are predicted to be unconnected, resulting in the relative isolation of these patches across multiple generations. This has implications for Ireland’s future conservation efforts as they may have to conserve patches from more than one metapopulation. This means that conserving one patch may not demographically support the other, requiring additional attentions to ensure that marine protected areas are ecologically coherent and sustainable. This example serves as a demonstration of a combined modeling approach where the comparison between predicted distribution and dispersal maps can highlight areas with higher conservation needs.publishedVersio
The intertidal zone of the North-East Atlantic region: pattern and process.
The north-east Atlantic region is an area where
clades originating in the north Pacific (fucoids,
balanoids, littorinids, thaids, laminarians) collide
with clades from further south in the Atlantic
(e.g., patellids, trochids, chthamalids). At high
latitudes in the north, seaweeds dominate the
midshore zone of all but the most exposed
shores. Further south, midshore space-occupying
invertebrates (mussels and barnacles) win, facilitated
by grazing by patellid limpets that controls
algal recruitment; propagule pressure is much
less as fucoids become rarer, and juvenile growth
is slower due to environmental stress, thereby
reducing the probability of escapes from grazing
(Figure 2.4) (Ferreira et al., 2014, 2015a, 2015b).
Low on the shore seaweeds dominate space by
forming algal turfs or kelp or fucoid canopies.
These algae outpace the ability of grazing limpets
to control them in the low-intertidal zone. L.
digitata canopies can lead to rock covered by
encrusting algae and sponges, facilitating
limpets. If canopy is removed, then colonising
ephemeral algae and turf-forming algae swamp
the limpets. There is usually too much water
movement immediately either side of low water
for effective foraging by sea urchins. Psammechinus
miliaris and Echinus esculentus only appear in
the subtidal, and Paracentrotus lividus is confined
to refuges in burrows relying mainly on the drift
of food (Benedetti-Cecchi and Cinelli, 1995;Boudouresque and Verlaque, 2007; Jacinto and
Cruz, 2012).
High on the shore, physical factors dominate.
At high latitudes in the north of the Atlantic,
ephemeral algae are present all year round. Further
south they are only present in the winter,
dying-off in the summer. Grazing has limited
effects, only occurring around refuges that
littorinids maintain (Stafford and Davies, 2005;
Skov et al., 2010, 2011).
Patterns are also strongly modified by mesoscale
processes driven by upwelling that influences
nutrient and larval supply (North Africa,
Iberia) and coastal configuration, where embayed
versus headlands also strongly influence larval
supply (France northwards). In high-recruitment
areas, interactions can be intense between spaceoccupying
species, also driving predator abundance
(e.g., dog whelks). Connell’s (1961a) classic
paper on competition was possible on the Isle of
Cumbrae because space was almost saturated;
elsewhere lower larval supply would have created
less intense interactions, as shown by Gordon and
Knights (2017) in Plymouth.
The north-east Atlantic has faster rates of
warming than any other ocean, although the
region south of Greenland and Iceland is undergoing
cooling due to a climate-driven slowdown
in the Atlantic meridional overturning circulation,
causing a weakening in the Gulf Stream
(Rahmstorf et al., 2015).
Species are responding to rapid alterations in
the marine climate by adapting or exhibiting
range shifts, or by becoming locally extinct.
There is a high degree of spatial and temporal
heterogeneity in the resultant impacts on marine
communities due to the idiosyncratic responses
of individual species. Warming seas have resulted
in biogeographic range shifts of intertidal and
subtidal species in coastal waters of the northeast
Atlantic. The leading range edges of Lusitanian
species are expanding, while the trailing
edges of boreal species are retracting to higher
latitudes, but with some cold-water species showing
surprising resilience (Southward et al., 1995;
Mieszkowska et al., 2006, 2014b; Lima et al.,
2007; Hawkins et al., 2008, 2009; Wethey and
Woodin, 2008; Mieszkowska and Sugden, 2016).
In addition to changes in the distribution ofspecies, community structure is also altering as
species dominance and interactions change
(Poloczanska et al., 2008; Hawkins et al., 2008,
2009; Mieszkowska et al., 2014b).
In a warming world the midshore of France
and the British Isles are likely to show much less
cover by large canopy-forming fucoids as harsher
warmer, drier and stormier conditions coupled
with increased grazing pressure from more
grazing species reduces the probability of fucoids
recruiting to form adult populations. Lowshore
kelp forests will likely change with less L. digitata
and A. esculenta and more S. polyschides. The late
autumn to early spring window of dense
ephemeral algal growth high on the shore (Hawkins
and Hartnoll, 1983a) will also constrict,
except in the north and in extreme exposure.
These changes will have consequences for biodiversity
(Thompson et al., 1996; Smale et al.,
2013; Teagle et al., 2017) and productivity (Hawkins
et al., 1992) – particularly the decrease in
export of algal detritus (Notman et al., 2016).
More shores will become dominated by
suspension-feeding barnacles and mussels. Thus,
there will be switches on many mid-latitude
shores as many become net importers rather
than exporters of energy (Hawkins et al., 2008,
2009)