Extract from favourable condition table for Fleet and Chesil European marine site (from English Nature 1999)

NB - Many of the attributes will be able to be monitored at the same time or during the same survey. The frequency of sampling for many attributes may need to be greater during the first reporting cycle in order to characterise the site and establish the baseline.

Feature

Sub-feature

Attribute

Measure

Target

Comments

Lagoon    

Extent

Area (ha) of lagoon basin, measured once per reporting cycle. No decrease in extent from an established baseline, subject to natural change. Extent is an attribute on which reporting is required by the Habitats Directive. The Fleet is a large lagoon, thus size (including the length:width ratio) will critically influence the hydrography of the site. Natural gradual reduction in area of the lagoon is inevitable, however, as a result of the natural progression of Chesil Bank.
   

 

 

Salinity

Seasonal averages encompassing the east-west salinity gradient measured periodically throughout the reporting cycle (frequency to be determined). Average seasonal salinity, and seasonal maxima and minima, should not deviate significantly from an established baseline, (to be derived from the Environment Agency monitoring programme), subject to natural change. Salinity is a key structuring factor within lagoons and in the Fleet, the gradient from west to east is particularly notable. Note should be made of natural fluctuations that occur according to year on year variations in rainfall.
   

 

 

Water clarity

Average light attenuation measured periodically throughout the reporting cycle (frequency to be determined). Average light attenuation should not deviate significantly from an established baseline, subject to natural change. Water clarity is important for maintaining the extent and density of algal and plant dominated communities. Clarity decreases through increases in amounts of suspended organic/inorganic matter.
 

 

 

 

 

Nutrient status -green algal mats

Extent across whole or parts of site, measured during summer months, annually. No increase in extent of green algal mats from an established baseline, subject to natural change. Nutrient status is important for the structure and functioning of the lagoon and its communities. The Fleet is probably naturally hypertrophic. Opportunistic green algae compete with other vegetation and affect the associated species. A late spring/early summer increase in filamentous green algae may be a related natural phenomenon or may indicate eutrophication.
   

 

 

Characteristic species - Rissoa membranacea membranacea

Population size - average abundance (number of individuals/m2), measured during the summer twice per reporting cycle. Average numbers should not deviate significantly from an established baseline, subject to natural change. Algal grazers (largely gastropods) affect the structure of the lagoon communities by consuming benthic and epiphytic growth. R.membranacea is the only species amenable to quantitative survey and can be used as a surrogate for grazers as a whole.
   

 

 

Characteristic species - Lamprothamnium papulosum (foxtail stonewort)

Density (number of plants/m2) and westward extent, measured during summer, twice per reporting cycle. Average density should not deviate significantly from an established baseline (to be derived from Holme (in press), Martin (pers. comm.) and 1999 seagrass survey) subject to natural change.

No eastward movement in westward limit.

The foxtail stonewort (L. papulosum) is a species characteristically found in lagoons which requires low nutrient conditions, particularly of phosphates, and therefore provides a possible indicator of nutrient status. It is a nationally scarce species.
   

 

 

Fish species assemblage

Number of composite species

measured during mid-summer from the inlet channel, once per reporting cycle

Average number of composite species should not deviate significantly from an established baseline, subject to natural change. Diverse fish community characteristic of large, inlet type lagoons, the sheltered conditions providing a nursery for a number of species. The fish community as a whole provides an integrated measure of the quality and functioning of the Fleet as well as indicating populations of the main predators.
   

Seagrass bed communities

Extent Total area (ha) of seagrass measured during peak growth period (Aug), twice per reporting cycle. No decrease in extent from an established baseline (to be derived 1991 and 1999 surveys), subject to natural change. Seagrass (including tasselweeds) contribute to the overall community structure within the Fleet and both are characteristic, to varying degrees, of lagoons. The area of seagrass provides a long-term integrated measure of environmental conditions.
   

 

 

Characteristic species - density of Zostera marina and Ruppia spp.

Density (number of shoots/ m2) measured during peak growth (Aug), twice per reporting cycle. Average shoot density should not deviate significantly from an established baseline, subject to natural change. Reduction in the density of plants is an early indicator of seagrass under stress and reflects changes in biomass. Zostera marina, Ruppia cirrhosa and R. maritima co-occur in many parts of the Fleet. Monitoring both Zostera and Ruppia may be justified as they have different salinity range preferences and therefore would provide an indication of conditions in different areas along the Fleet.
   

Tide-swept communities

Tide-swept communities - species composition Presence and abundance of composite species, measured during summer, once per reporting cycle. Presence and abundance of composite species should not deviate significantly from an established baseline, subject to natural change. Tide-swept communities are characteristic of inlet lagoons and are therefore integral to the structure of such lagoons. The bedrock biotope, which includes a number of rare or southern species such as the sponge Suberites massa, is the most notable part of the community and potentially provides a long-term integrated indication of tidal flow of the Fleet and therefore of a key functional process.
   

Subtidal coarse sediment (gravel, cobbles, pebbles) communities

Extent Area (ha) of submerged coarse sediment (gravel, cobbles & pebble) communities, measured once per reporting cycle. No decrease in extent from an established baseline, subject to natural change. Extent of sediments in this part of the Fleet indicates proportion of a habitat that adds to the structural diversity of the site and is likely to reflect hydrological conditions.
 

 

 

 

 

Characteristic species - density of Anemonia viridis

Density (number of animals/m2), measured during summer once per reporting cycle. Average density should not deviate significantly from an established baseline, subject to natural change. The stability of the sediments enabling a diverse community to develop is notable. Monitoring of the community indicates condition of a distinct section of the Fleet and of water movement etc between the mouth and the Narrows. Unusually, the anemone Anemonia viridis occurs in high numbers and can therefore be readily measured. The species should be used as a surrogate for the community as a whole and indicator of a change in conditions.
   

Intertidal sediment communities

Extent Area (ha) of intertidal sediment between the Narrows and Smallmouth, measured once per reporting cycle. No decrease in extent from an established baseline, subject to natural change. Extent of sediments in this part of the Fleet indicates proportion of a habitat that adds to the structural diversity of the site and is likely to reflect hydrological conditions in the entrance to the Fleet.
   

Intertidal sediment communities

Species composition Presence and abundance of composite species, measured during summer once per reporting cycle. Presence and abundance of composite species should not deviate significantly from an established baseline, subject to natural change. The infaunal community, which includes a number of rare and/or lagoonal specialist species, eg A.cirrhosa, is indicative of sheltered, fully saline conditions and is likely to change in relation to a number of factors including hydrological conditions in the entrance to the Fleet.
   

Shingle spring line communities

Extent and distribution Frequency and distribution of shingle springline communities, measured during summer, once per reporting cycle. No decrease in extent from an established baseline, subject to natural change. The spring line community is unusual and reflects both the stability of, and percolation through, the shingle bank. The extent of the community (as measured by distribution) will be indicative of saline seepages along much of the Chesil Bank
   

 

 

Species composition

Presence and abundance of composite species, measured during summer once per reporting cycle. Presence and abundance of composite species should not deviate significantly from an established baseline, subject to natural change. The spring line community, which includes notable species such as Caecum armoricum (De Folins lagoon snail), is unusual and reflects both the stability of, and percolation through, the shingle bank. As such the community adds to the diversity (structure) of the lagoon and will reflect processes in relation to both the shingle and percolation of sea water into the lagoon.

NB .Extreme events (such as storms reducing or increasing salinities, exceptionally cold winters or warm summers) also need to be recorded as they may be critical in influencing ecological issues in the Fleet and may well be missed by routine monitoring

 

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Glossary of terms used in the favourable condition table

Feature The habitat or species for which the site has been selected.

Sub-feature An ecologically important sub-division of the feature.

Attribute Selected characteristic of an interest feature/sub-feature which provides an indication of the condition of the feature to which it applies.

Measure What will be measured in terms of the units of measurement, arithmetic nature and frequency at which the measurement is taken. This measure will be attained using a range of methods from broad scale to more specific across the site.

Target This defines the desired condition of an attribute, taking into account fluctuations due to natural change. Changes that are significantly different from the target will serve as a trigger mechanism through which some further investigation or remedial action is taken.

Comments The rationale for selection of the attribute.

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