 |
||
Monitoring Climate ChangeThe following extracts demonstrate Fair Isle's important role in monitoring climate change and its effects on the ecosystem, with changes in sea temperatures, salinity and weather data, and can all be found in their original form in our FIMETI Newsletters 'Making Waves' . Extracts are in chronological order, beginning in 2005 and continuing through to 2015.
Photo: Fair Isle Wildlife Club sampling for plankton at North Haven. FIMETI Newsletter no. 4 Aug 2005 What is happening to our seas? The following two notes draw on recent studies which suggest that physical factors are driving some of the changes we have been observing in our marine ecosystem. Changes in the Plankton community There is a long run of data for the plankton of Fair Isle waters thanks to the UK Continuous Plankton Recorder survey, which has been operated in the North Sea since 1931. These data demonstrate considerable changes in the diversity and composition of plankton in recent years, linked to sea temperature changes and their effect on currents and plankton populating those currents. Lindley & Batten (2002), studying CPR results for the period 1958- 1995, reported that in the final decade of that period (1986-95) there was an inflow of species associated with warm oceanic waters into the North Sea which modelling showed was via the Fair Isle passage. This inflow was much greater than in previous years, and included an abundance of three warmer water species, two of which had not been recorded prior to 1986. The study pointed out that these biological indications of change were supported by hydrological data such as high salinity anomalies and higher temperatures. By contrast, resident and colder water holoplanktonic species had declined in abundance. The authors questioned whether the increased species richness of the addition of these more southerly or Atlantic species can be accepted as a positive biodiversity measure as the newcomers were largely temporary constituents of the community and therefore of less “value” to the trophic stability (food chain) of the regional ecosystem. It is known that the population dynamics of such key species as sandeels are affected by environmental conditions as well as fishing impacts, and the current worrying decline in Fair Isle seabird breeding success may, in part at least, reflect wider climate change impacts on the marine ecosystem. Climate change Fair Isle is strategically placed to monitor changes in climate, and their associated effect on Scottish coastal waters. It was not surprising therefore, that Fair Isle featured strongly in the Scottish Ocean Climate Status Report 2000-2001 (published by the Scottish Executive Fisheries Research Services in May 2003). The value of the long run of data collected by Dave Wheeler of the Fair Isle Meteorological Station was demonstrated by the use of Fair Isle sea- surface temperature data in the report, alongside similar runs of data from Peterhead on the Scottish east coast and Millport in the west. These demonstrated that from the mid 1990s, mean monthly temperatures were consistently above the long-term monthly averages at Fair Isle and Millport, an upward trend which was less obvious from Peterhead data. The Fisheries Research Services also selected the Fair Isle Current as an indicator of the changes in the exchange of water between the Atlantic and the North Sea. This showed year to year periods of temperature and salinity increase and decrease over the period 1970-2001, superimposed on longer- term trends. However, the Fair Isle Current data showed consistently above long-term mean temperatures since 1996 whereas the long-term trend for salinity is downwards, with surface salinity decreasing during 2000 and 2001 to the lowest values since measurements began (1970). The report indicated that Fair Isle lay in a band whose surface water temperature had risen by 0.2- 04°C per decade during the period 1981- 2000. The same report showed a map of temperature trend derived from a climate model which predicted further increases of similar value per decade in the period 2001- 2020. FIMETI Newsletter no. 6 April 2008 CLIMATE CHANGE
Graph: Fair Isle - Sea Surface Temperature for 2007 and 1974-2000 Mean. Courtesy Dave Wheeler, 2008. Sea temperatures recorded in North Haven during the early part of 2007 were above normal, but during the late summer and autumn they were below normal (see above). Further graphs and analysis of seasonal sea surface temperatures recorded on Fair Isle between 1968 and 2007 are soon to be included in the Marine Database section of the FIMETI website at http://www.fimeti.org.uk. FIMETI Newsletter no. 7, March 2010 Wildlife indicators Populations of a whole suite of insects, and other fauna and flora, are extended their range northwards during this period of accelerating climate change and some are making it as far north as Fair Isle. This expansion is not confined to terrestrial species. The rare small cushion star Asterina phylactica was previously known only as far north as the Inner Hebrides, so the discovery of one near South Light by Henry Hyndman in April 2009 is a significant extension northwards.
Henry Hyndman, the sharp eyed young Fair Islander with his find. The cushion star was full-grown despite measuring only 10 mm across. Photos Copyright Liz Musser. In October, there was an unprecedented wreck of thousands of the mauve stinger jellyfish Pelagia noctiluca washed ashore on North Haven beach, with many others noted in the geos and offshore. This species has only been seen on a handful of occasions on the isle before, and never in such numbers. This species is commonly encountered as far south as the Mediterranean, though it is known from deeper Atlantic waters too. Extreme prolonged south-westerly winds may have played a part in forcing them to our shores.
The Mauve Stinger Pelagia noctiluca. Photos copyright Elizabeth Riddiford & Deryk Shaw. Fair Isle has long been known for its changeable weather and we certainly saw this in 2009. September, prior to the jellyfish invasion, was marked by a succession of strong west to south-west winds with rain, and the summer was notable for its extreme dry conditions. There was a general consensus amongst islanders, including those with the longest memories, that the ground was the driest they had known for many years and even boggy parts of the Hill which previously would not carry the weight of a man were walkable in ordinary shoes – though, in demonstration of how memory can play tricks, Dave Wheeler of the Fair Isle Weather Station indicates that such conditions have prevailed before, such as in the 1970s (Figure 8). Dave recognises a pattern of greater variability in overall weather conditions (as per rainfall example, Figure 8) and this must challenge the tolerance levels of plants and animals alike.
Figure 8. Annual rainfall fluctuations around a 37-year mean, Fair Isle (courtesy of D Wheeler, Fair Isle Meteorological Station). So, for instance, mean sea temperature has risen by a degree over the last 40 years but superimposed on that are shorter term seasonal and annual fluctuations (see Figure 9) which will have a bearing on plankton ecology and populations.
Figure 9. Seasonal and annual sea surface temperature trends and fluctuations over a 44-year period, Fair Isle (courtesy D Wheeler, Fair Isle Meteorological Station). Fair Isle has had prolonged periods of westerly winds before, so the major invasion of a jellyfish not previously recorded in such numbers inshore may also reflect changes in its population due to climate factors rather a shorter term weather event. MONITORING THE SEA The Fair Isle Weather Station collects a small range of sea data on a regular basis. This capacity is about to be expanded in both range and regularity. The Aberdeen marine laboratory is setting up an automatic recording gauge in North Haven which will record surface sea temperature, salinity, nitrates, phosphates, silicates, phytoplankton, wave height and frequency and sea levels. It also incorporates an automatic weather station recording air temperature, pressure, wind speed and direction. This is an excellent addition to the suite of physical and environmental data monitoring activities already underway on the isle. Weather patterns (with thanks to Dave Wheeler) The Fair Isle meteorological station has a long and enviable set of data including for surface sea temperatures. The data clearly show a steady if slow increase in mean temperatures over the last 30 years. However, there is a suggestion that this increase may have ceased, at least temporarily, and may even have reversed. These data are currently being evaluated by a statistician to ascertain whether the apparent trend is significant. Another interesting pattern, which may surprise folk familiar with shipping forecasts, is that mean wind speeds have been lower in the last decade by some 1.5 to 2 knots (3-4 m per second). FiMETI Newsletter no. 8, March 2011.
Photos: Left - Sand creeplet anemone, Right - Little cuttlefish. Copyright TH Hyndman There has been a trend of discoveries in recent years of “southern” species, including biota well north of their previous known range. This trend continues, emphasizing the biogeographical importance of Fair Isle during this period of flux. The enthusiasm and sharp eyes of children contribute to these discoveries and that was the case in March 2010 when an eight-year old resident found the tiny sand creeplet anemone Epizoanthus couchi. The UK marine database, MarLIN, records it as occurring no further north than the NW corner of mainland Scotland. This record extends the distribution nearly one degree farther north (more than 100 km to the north-west). Climate change is not just about linear temperature increases. Other impacts include falling salinity levels, rapid seasonal fluctuations in sea temperatures, increased acidity in the sea and changes in weather patterns. These all put enormous pressure on the marine ecosystem and reduce biodiversity to a narrow suite of species capable of tolerating greater extremes. FIMETI Newsletter no. 9 (March 2012) Climate change There was a whole series of occurrences in 2011 which may be linked to climate change. Species moving north
In 2009 a small cushion star Asterina phylactica was discovered at Shalstane, a major range extension northwards for this species. The discoverer, ten-year-old Henry Hyndman, re-visited the site this year (2012) and found that a colony of 25, all within a small area had become established. Some were laying eggs. Oceanic currents In late July there was another influx of plankton into North Haven, including a number of jellyfish and their allies. They included the spectacular Physophora hydrostatica, an amazing combination of orange body, transparent tubes ending in a narrow cylindrical float and a trail of yellow droplets held by threads below – giving it the English name of “hula skirt siphonophore”. It is a deep sea species but, being a slow swimmer, is vulnerable to being swept to the surface by currents. Five were collected, and there were many more.
Other species present included the blue jellyfish Cyanea lamarckii – which occurs from time to time; mauve stinger Pelagia noctiluca – which normally occurs further out to sea (but there was a massive invasion in autumn 2010); a number of the comb jelly Bolinopsis infundibulum – a very common summer visitor to Fair Isle shores; and Ptychogena crocea - a thecate hydroid usually found on rocky substrates well below the tidal zone. Neither the Physophora nor the Ptychogena had been recorded previously for the isle. The influx also included numerous smaller plankton. By far the most numerous was a Calanus copepod – probably Calanus helgolandicus which is a recent late summer invader of our waters (replacing Calanus finmarchicus which has disappeared in response to climate change). The most interesting capture was a blue and green coloured copepod called Anomalocera patersoni. The blue markings appeared luminescent in some lights. This is a surface waters dweller of North Atlantic origin, quite widespread but having suffered a major decline in population since the 1970s. The components of this influx appear to comprise largely pelagic species of Atlantic oceanic origin. Their exceptional arrival inshore may be linked to changes in strength or pattern of ocean currents. Extreme weather
The outermost part of a rocky platform which forms the southern “barrier” to Shalstane is normally dominated by a carpet of mussel Mytilus edulis spats. This was not the case in 2011. Apart from those in fissures and cracks, the carpet had completely gone; an estimated two years of spats had been eliminated. The reason is unknown. However, in the Solway (south-west Scotland), mussels and cockles are vulnerable to severe frosts leading to occasional major population losses (S Wilson, cockle-picker and former Fair Isle resident, pers. comm.). Winters 2009/10 and 2010/11 have been particularly severe on Fair Isle, at least in comparison with the recent winter norm, with snow lying even on the outer stacks. The loss of spats is perhaps best explained by their vulnerability to these severe conditions, with those hidden within the cracks experiencing a less lethal micro climate regarding exposure to sub-zero temperatures.
In December 2011, islanders noted that the colour of the dominant lichen of the walls, sea ivory Ramalina siliquosa, had turned red. In the more exposed areas this classic lichen of maritime habitats was largely rusty red on the windward west-facing wall, but the usual glaucous grey-green on the eastern leeward side. This formerly rare occurrence has become far more frequent in recent years. A similar occurrence on the Hill Dyke was noted in February 2010; and there was one particularly severe event in the mid 1990s – the first time it had been noted. This event always occurs after a prolonged period of very high winds with no or little accompanying rain. Thus the lichen gets a heavy dose of salt which clearly affects it. However, it does not kill the lichen although it does take up to several months to return to its former colour. What seems to be happening is that the algal partner, which is the green element (as its role is the photosynthesis), is wiped out – perhaps because the salt lowers moisture levels to the extent that the alga cannot survive. The recovery of the lichen to its former colour must mean that the fungus can capture and nurture free-living algal cells or spores; or perhaps just a few algal cells survive within the plant but take time to re-populate fully. Extreme weather events of this sort appear to be becoming more frequent. FIMETI Newsletter no 12, March 2015 (page 19) Reflections on Fair Isle ecosystem dynamics in 2014 The marine ecosystem in 2014 - implications for research The fish and seabird summaries in this latest newsletter indicate a sudden and considerable change in the local ecosystem. Fortunately, the isle has a 50 year run of climate data, held by Dave Wheeler at the Fair Isle Meteorological Station, including surface sea temperature and salinity levels. For the last 40 years there has been a gradual but steady mean sea temperature increase of approximately 0.1° celsius per decade. In 2014, however, the mean sea temperature in late spring was 2° below the long-term mean – a change first noted the spring before. The hypothesis that the warmer waters had driven zooplankton such as Calanus finmarchicus to cooler water farther north – leading to severe disruption to the food chain – is further supported by the coincidental nature of a sea temperature dip and a return to a more dynamic ecosystem; as demonstrated by seabird success and the density of small fish. No direct monitoring of plankton availability was done, but qualitative information in the guise of numerous fulmars close inshore in calm weather successfully picking food items off the sea surface, pecking to left and right at a rate of 4 or 5 pecks per second, suggested that zooplankton levels were high. Dave Wheeler considered that the drop in sea temperatures could be attributed to the effects of the Greenland ice melt, with a tongue of cold water extending down to northern Britain. Should this be the case, the beneficial effects of cooler temperatures may be relatively short-lived. A major component of the research programme proposed by FIMETI is to use Fair Isle’s large and wide-ranging long-term datasets to get a fuller understanding of the contributory factors affecting the functioning of the ecosystem. The changes witnessed in 2014 make this even more needful and apposite. The isle sees such a study as beneficial on a Scotland-wide scale, for sustainable marine management, environmental conservation and the fishing industry. In addition to Fair Isle data, additional long-term datasets such as the Continuous Plankton Recorder managed by the Sir Alister Hardy Foundation for Ocean Science and physical oceanographic data can be made available. There can be few places in Scotland so ideally situated and so rich in scientific data as Fair Isle. LINKS WITHIN THIS WEBSITE Fair Isle Dossier - A baseline for developing MPA management.pdf (includes Seabird Data Charts and Sea Surface Temperature Data Charts) For further information about the collection and recording of Fair Isle climate data please also see - FAIR ISLE WEATHER STATION
Text and photographs Copyright Fair Isle Marine Environment and Tourism Initiative. All rights reserved.
|  |
|
