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Of the invertebrate groups encountered during the 2001 sampling season only theÌýcladocerans,ÌýchironomidsÌý²¹²Ô»åÌýcopepodsÌýwere examined in any detail. Some field notes were made concerning representatives of other groups (see below).

Introduction

Worms

Annelida (Segmented Worms)
Both oligochaetes and leeches were recorded in some of the surveyed sites. Specimens of small red worms (‘thread worms’ tubificids?) were observed under stones in Long Pond and Goose Pond and these were fairly abundant at the former, a site with a pH <5. Leeches were scarce with several small specimens being found in North Sulivan Lake and North Valley Pond on the underside of stones. Also see Simpson & Nolan (1994).

Platyhelminthes (Turbellaria)
Specimens of planarian-like flatworms were occasionally found in the 2001 survey attached to the underside of stones selected for diatom sampling. Sites where flatworms were present are North Sulivan Lake and Goose pond.

Crustacea

Amphipoda (Gammarid shrimps)
The gammarids or freshwater shrimps are common in some of the lowland ponds. They are generally represented by small-bodied species with specimens being up to about 1 cm long. Their laterally compressed body allows them to creep underneath stones where they are most often found. They were not found in the most acid sites and were most common at the pH 6-7 sites, such as North Sulivan Lake, Mutton Pond, Top Hog Pond, Laguna Isla, Swan Inlet and especially in Cheroogs Pond and Goose Pond. A few larger-bodied forms occurred in East Arm Pond. At the upland sites, none was found in Adam Tarn but a few were present in or near aquatic mosses in the lower altitude Little Adam Tarn. Of the flowing waters, only Halfway House stream possessed an abundant gammarid population. However, in the Warrah, San Carlos and Malo rivers only a few specimens were collected despite multiple kick sampling.

The amphipods are an interesting group in the Falklands because they comprise two (Praefalklandella) species that are endemic to the islands (Stock & Platvoet 1991) but were only found in stream samples. The other two (Hyalella) species are found also in Patagonia.

Decapoda (Prawns, Crayfish)
None found.

Ostracoda (Bi-valved Crustaceans)
This group of bivalved crustaceans is reported as present (Simpson & Nolan 1994) but representatives were absent from the acid sites surveyed in this study. However, at the circum-neutral sites, lake or pond surface sediments contained an abundance of ostracods. Sites where ostracods (mainlyÌýCandonaÌýspp.) were common include Top Hog Ground Pond and Hawks Nest Pond on West Falkland. A few specimens also were present in kick samples from the River Warrah. With Cladocera (water fleas), this group is typically a food resource for predatory invertebrates and fish but is not usually exploited directly by water birds.

Mysidacea (Marine Shrimp)
This group was very scarcely represented. Only two individuals were observed in the deep water sample from Adam Tarn. They resembledÌýMysis relictaÌýbut were small being about 1.5 cm long and were almost transparent.

Aquatic insects

Odonata (Dragonflies and Damselflies)
Representatives appear to be absent from the Falkland Islands sites visited.

Trichoptera (Caddis Flies)
Small cased caddis larvae were moderately abundant in several sites on the underside of stones, particularly in Halfway House stream and Kings Ridge Pond. They were noted occasionally also in Cheroogs Pond, Wall Pond, Wireless Ridge Pond and Little Adam Tarn.

Plecoptera (Stoneflies)
None were found in the 2001 survey but see McLellan & Wais (1990).

Ephemeroptera (Mayflies)
None were found in the 2001 survey but R.M McDowell (pers. comm.) has reported finding several specimens near Hawks Nest Pond. However there remains a possibility that they were brought on to the island with sampling equipment.

Heteroptera (True Bugs)
None were observed.

Culicidae (Mosquitoes and Gnats)
Very few mosquito larvae were found in several sites. In Dan’s Shanty Pond, a small peaty pool on East Falkland, a few mosquito larval pupae were observed. It is to be expected that most of the many small pools in the area possess some mosquito larvae but no adults were seen and larval specimens are generally rare.

Dytiscidae (Diving Beetles)
A few specimens of dytiscid beetles were noted in Sulivan South Lake, Mutton Pond and in Dans Shanty Pond (also see Simpson 1991).

Molluscs

Very few bi-valve molluscs were found in the Falkland sites sampled, reflecting the acidic nature of most of the sites in the 2001 survey. A few individuals, probablyÌýPisidiumÌý(Pisidium plenilunium, M. Simpson, pers. comm.) only 2-3 mm in diameter, were found in East Arm Pond. Gasteropod molluscs were however common at some of the richer sites,ÌýLymnaeaÌýappeared to be represented by two species (see Simpson & Nolan 1994) and the larger one was particularly common in Halfway House stream.ÌýLymnaeaÌýalso commonly occurred in Laguna Isla, Top Hog, and Valley North Pond. Some very small gasteropods, probablyÌýHydrobia, were present at Rosalie Stream and several other sites with brackish connections.

References

• McLellan ID, Wais IRÌýet al.Ìý(1990) The first record of Stoneflies from the Falkland Islands, Aquatic Insects 12: 177-180.
• Simpson MN (1991) Aspects of Falklands freshwater ecology. The Warrah: News Letter of Falklands Conservation 1: 8-10.
• Simpson MN & Nolan RJ (1994) Freshwater Ecology in the Falkland Islands. Falklands Islands Journal 1994, 1-4.

Stock JH & Platvoet D (1991) Freshwater amphipods of the Falkland Islands. J. Nat. Hist. 25: 1469-1491.

Cladocera

This group of crustaceans (commonly known as water fleas) was frequently represented in most samples from most of the pond and lake sites we visited. They occurred in both plankton hauls from the deeper sites (North Sulivan Lake and Adam Tarn) and in water/kick samples from near lake or pond margins. Cosmopolitan typical planktonic species present areÌýEubosmina longispinaÌý²¹²Ô»åÌýBosmina longirostrisÌýand these occurred at most sites. Also,ÌýDaphnia pulexÌý²¹²Ô»åÌýD. longispinaÌýwere sometimes common.

The large predatory cladoceran,ÌýLeptodora kindtiÌýwas noted in just two sites, Mappa Pond and Goose Pond (East Falkland) andÌýKurzia cf. latissimaÌýoccurred only in North Sulivan Lake. Chydorus taxa,ÌýAlona guttataÌýand largeÌýA. affinisÌýwere sometimes common.ÌýChydorus pigerÌýwas most common in North Sulivan lake and was collected near aquatic plants (SE end of the lake). These species are tolerant of acid water and low calcium concentrations and ecologically can be considered non-specialist organisms. Some species are typical of acid upland sites in the UK (Fryer 1993) but the harsh conditions in the Falklands allow these taxa to persist at low altitudes andÌýA. affinisÌýis common in Swan Inlet, a site near sea level.

None of the species identified seemed to be typical of the Subatlantic region, however, several taxa were not identified confidently andÌýµþ´Ç²õ³¾¾±²Ô²¹Ìýcf.Ìý°ì±ð²õ²õ±ô±ð°ù¾±Ìý(Kings Ridge Pond),ÌýChydorusÌýsp. (San Carlos River),Ìý°ä±ð°ù¾±»å²¹±è³ó¾±²Ô²¹Ìýcf.Ìý°ù±ð³Ù³Ü²Ô»å²¹Ìý(goose Pond) andÌýµþ´Ç²õ³¾¾±²Ô²¹Ìýcf.Ìý±ô´Ç²Ô²µ¾±°ù´Ç²õ³Ù°ù¾±²õÌý(Lake Arthur) are, most likely, taxa that are restricted to the southern hemisphere.ÌýB. longirostrisÌýis also commonly found in Andean lakes (ModenuttiÌýet al.Ìý1998) and in oligotrophic sites in Europe.

Distributions of taxa common in inland waters of the Falkland Islands are indicated inÌýTable 1Ìý(note that not all sites visited were investigated for Cladocera).

Table 1.ÌýOccurrences of some common cladocerans were noted in 14 of the surveyed sites (* indicates stream sites).

Site	Bosmina	Daphina	Cerio- daphnia	Chydorus	Alona	Macrothrix	Simocephalus
Authur Lake	+++	Ìý	Ìý	Ìý	Ìý	Ìý	Ìý
Halfway House*	++	++	Ìý	Ìý	Ìý	Ìý	Ìý
Sulivan North	+	Ìý	Ìý	++	++	Ìý	Ìý
Red Pond	++	Ìý	Ìý	Ìý	+	Ìý	Ìý
Swan Inlet	Ìý	Ìý	Ìý	Ìý	++	+	Ìý
Hawks Nest	Ìý	Ìý	Ìý	Ìý	+	Ìý	Ìý
Goose Pond	Ìý	+++	++	Ìý	Ìý	+	+
Sand Pass	+	++	Ìý	Ìý	Ìý	Ìý	Ìý
Valley North	Ìý	Ìý	Ìý	++	+	Ìý	Ìý
Laguna Isla	++	Ìý	Ìý	Ìý	+	Ìý	Ìý
San Carlos*	Ìý	Ìý	Ìý	?	Ìý	Ìý	Ìý
Wireless Ridge	Ìý	Ìý	Ìý	+++	Ìý	Ìý	Ìý
Warrah*	Ìý	Ìý	Ìý	Ìý	+	Ìý
Kings Ridge	Ìý	Ìý	Ìý	Ìý	+	Ìý

References

• Fryer G ( 1993) The Freshwater Crustacea of Yorkshire. Titus Wilson & son, Kendal.
• Modenutti BE, Balseiro EG, Queimalinos CP, Anon DA, Dieguez MC & Albarino RJ (1998) Structure and dynamics of food webs in Andean lakes. Lakes and Reservoirs: Research and Management. 3: 179-198.

Copepoda

This group was relatively common and is represented by cosmopolitan species and by species that are restricted to South America or the Southern Hemisphere. Species within the centropagid genusÌýBoeckellaÌýwere commonly found in the Falkland sites; these copepods are often predatory and are restricted to the Southern Hemisphere (Menu-Marque et al 2001).ÌýB. michaelseniiÌýwas the most common copepod found in Falkland inland waters (Table 2) andÌýB. gracilipesÌý²¹²Ô»åÌýB. poppeiÌýwere also recorded. These species are also found in both Antarctic and Andean lakes (Hanson & Tranvik 1997, ModenuttiÌýet al.1998, Menu-MarqueÌýet al.Ìý2001).

Some copepod species are remarkably large (up to 5 mm long, e.g. in Laguna Babbas) and where water was clear (Adam Tarn) or slightly peat-stained (Dans Shanty Pond, Wireless Ridge Pond) these large copepods were bright red.ÌýParabroteas sarsiÌýwas the largest calanoid copepod present and is a species known also from Andean and Patagonian lakes (Modenutti et al. 1998). These large copepods are predatory on rotifers and other zooplankton including Cladocera.

The presence of such large zooplanktoners indicates a lack of fish predation. Several sites in the FIBRIL survey are probably fishless due to the high altitude and lack of access (Adam Tarn) or to seasonal desiccation (very shallow sites such as Laguna Babbas may well dry out in some summers). In addition, large copepods were not found in exposed sites with high turbidity such as Wall Pond, Lake Authur, and Red Pond.

The other common copepods are cyclopoids of the genusÌýAcanthocyclops, particularlyÌýAcanthocyclops michaelseniÌýwhich was abundant at sites such as Goose Pond and Laguna Isla.

Table 2.ÌýSome copepods are found in Falkland inland waters (* indicates stream sites).

Site	Boeckella michaelseni	Boekella gracillipes	Boekella poppei	Parabroteas sarsi
Red Pond	++	Ìý	Ìý	Ìý
Mutton Pond	+++	Ìý	+	Ìý
San Carlos*	++	Ìý	Ìý	+
Laguna Babbas	Ìý	Ìý	Ìý	+
Lake Arthur	Ìý	+

References

• Hanson LA & Trannvik L (1997) Algal species composition and phosphorus recycling at contrasting grazing pressure. Freshw. Biol. 37: 45-53.
• Menu-Marque S, Morrone JJ and Locasio de Mitrovich C (2001) Distributional patterns of the South American species of Boeckella (Copepoda: Centropagidae): a track analysis. Journal of Crustacean Biology 20: 262-272.
• Modenutti BE, Balseiro EG, Queimalinos CP, Anon DA, Dieguez MC & Albarino RJ (1998) Structure and dynamics of food webs in Andean lakes. Lakes and Reservoirs: Research and Management. 3: 179-198.

Chironomids

The Chironomidae are a family of small non-biting midges and species are relatively common in Falkland Island ponds and lakes. They occur throughout the world and about 6000 species are currently known. The adults are usually green or black and are not usually more than 1 cm in size. They are frequently seen near water, sometimes in large swarms. The males, recognisable by their plumed antennae, form swarms to attract females. They mate with them in flight. Adult chironomids usually do not feed and they do not bite humans.

Most species of chironomids lay their eggs in water. The eggs are held together in a small blob or string of jelly. Chironomid larvae are worm-like and live in a wide range of aquatic habitats but are most common in lakes or streams. Most species live inside a silk tube which they spin themselves. They graze on microscopic algae and bacteria. A few free-living chironomid larvae are carnivorous, eating other chironomids. Most chironomid larvae are yellowish or green but a few are bright red. These so-called blood-worms have the red pigment haemoglobin in their blood which allows them to live in water that is poor in oxygen. Oxygen-poor water is often polluted and contains large amounts of nutrients. Most animals cannot live in these conditions, so without competition and with plenty of food, bloodworms can often build up huge populations. This may cause problems for people living near a sewage treatment works when massive swarms of chironomid adults emerge. They are attracted to lights and may be a nuisance when they enter houses. Chironomid larvae usually complete their development in one year. They enter the pupal stage, which may last only a few days, and then the adult is ready to emerge.

Chironomids are very useful indicators of water quality. The larvae and pupae are easy to sample. The larval heads (Figure 1) are well-preserved in lake sediments so we can look at changes in chironomid populations back through time by analysis of lake sediment cores. Some species are indicative of good water quality others, like the bloodworms, are indicative of poor water quality. We can also deduce changes in past climate by analysis of chironomid larvae in sediment cores since some species are typical of cool conditions while others only occur when the climate was warm.

The following chironomid taxa were present in the 2001 Falklands survey samples:

• AblabesmyiaÌý(a carnivorous genus)
• MacropelopiaÌý(a carnivorous genus)
• ApsectrotanypusÌý(a carnivorous genus)
• ParochlusÌý(a genus typical of cool water)
• PodonomopsisÌý(a genus typical of cool water)
• ChironomusÌý(a blood worm)
• Phaenopsectra
• TanytarsiniÌý(two different species)
• CricotopusÌý(three different species in this genus)
• ParapsectrocladiusÌý(a genus previously thought to be restricted to Patagonia and southern Chile (Cranston, 2000)

Other taxa that have been recorded from the Falklands by Dr Peter Cranston (the University of California, in Davis, USA) are:

• RheotanytarsusÌý(a genus of running water)
• PodonomusÌý(a genus typical of cool water)

Some elements of the chironomid fauna of Patagonia, together with biogeographical considerations were reviewed by Brundin (1967).

References

• Brundin L (1967) Transantarctic relationships and their significance, as evidenced by chironomid midges, with a monograph of the subfamilies Podonominae and Aphroteniinae and the austral Heptagyiae. Kungl. Svenska Vetenskapsakademiens Handlingar 11. 1-472.
• Cranston PS (2000)ÌýParapsectrocladius: a new genus of orthocladiine Chironomidae (Diptera) from Patagonia, the southern Andes. Insect Systematics and Evolution 31: 103-120.

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