Lowland freshwater swamps, in contrast to marshes, are forested perennial lowland wetlands (Figure 5.5.14), with their water depth often fluctuating on a seasonal basis due to influxes of limnetic water from perennial streams. This ecosystem category includes a range of botanically diverse coastal plain and riparian forested wetlands, including sago swamps, pandanus swamps, and peat swamp forests, all of which are extensively represented in Papua, particularly along the southern coast bordering the Arafura Sea. Peat swamp forests could potentially be segregated as a separate ecosystem on the basis of acidic water chemistry, similar to the case with upland bogs. Distinguishing flora includes Metadina, Barringtonia, sago (Metroxylon sagu), various Pandanus species (for list see Stone, 1982), and Campnosperma brevipetiolata in very wet areas. Also assignable here are the ‘‘freshwater mangrove’’ forests, florally dominated by Myristica, Callophyllum, Syzygium, Campnosperma, Palaquium, Intsia and Diospyros, and similar riparian forests of Sonneratia caseolaris (for additional discussion see Johns 1982 and Chapter 5.7). This is prime habitat for certain fishes such as blue-eyes (Pseudomugil), and gudgeons (Oxyeleotris and Mogurnda). Typical insect fauna includes Odonata in the families Protoneuridae (Nososticta) and Libellulidae (Agrionoptera, Orthetrum), and Heteroptera in the families Gerridae (Limnometra, Rhagdotarsus), Veliidae (Microvelia, Strongylovelia), Hydrometridae (Hydrometra), Veliidae (Microvelia), Belostomatidae (Appasus), and Nepidae (Ranatra).

      Saline Lowland Wetlands

      Lowland saline marshes, more commonly known as salt marshes, are non-forested lowland saline wetlands dominated by emergent vegetation, most characteristically Pickleweed (Batis maritima). Lowland saline swamps, by contrast, are forested lowland or riparian saline wetlands dominated by a diverse array of mangrove species (Figure 5.5.15), and often intergrade into true euhaline mangrove estuaries. Such mixohaline swamps support mixed floral assemblages of Avicennia, Nypa, Rhizophora, Bruguiera, and Sonneratia (for further discussion see Johnstone and Frodin, 1982), and a characteristic surface insect fauna (J. Polhemus and D. Polhemus 1996; Andersen 1992; Andersen and Weir 1999) of trepobatine Gerridae (Stenobates, Rheumatometroides) and haloveliine Veliidae (Xenobates). Salt marshes and mangrove swamps of these types are common along the coasts of Papua, with the latter extensively developed bordering the Arafura Sea, along the margins of Bintuni Bay, and at certain river mouths along the north coast. They are discussed more extensively in Chapter 5.4.

      Also falling within this ecosystem class are various intermittent lowland wet-lands, consisting of lentic waters occurring seasonally in shallow basins. Their waters are generally warm (20–30 C), mixohaline or poikilohaline (although evaporation may cause such waters to become hyperhaline as drying progresses), and basic, with pH values of 6.5–8.0. Characteristic biota includes certain littoral halophilic insects, including Diptera in the family Ephydridae (Ochthera) and Heteroptera in the family Saldidae (Pentacora, Saldula). Fishes may also be present, especially blue-eyes and various gudgeons. Examples of such ecosystems in Papua include certain seasonally dry lake basins formed between limestone anticlines east of Kaimana in the Vogelkop region, and salt pans that border the back margins of mangrove estuaries along the southern New Guinea coast.

      Anchialine Pools

      An additional type of saline lowland wetland ecosystem found to a limited degree in Papua consists of anchialine pools. The name (from Greek anchialos, ‘‘near the sea’’) was suggested by Holthuis (1973) to define ‘‘pools with no surface connection to the sea, containing salt or brackish water, which fluctuates with the tides.’’ Such pools contain a distinctive biota consisting most typically of invertebrates of marine origin that have invaded through subterranean interstices, and often support unusual taxa not found elsewhere, particularly red shrimps, with fishes being rare or absent. These pools are generally small, with the majority being less than 100 m² in area. Their surfaces are usually inland extensions of the oceanic water table, although mixohalinity, usually less than 10 percent, often results from dilution by seaward percolating groundwater. Ecosystems of this type, sometimes referred to as ‘‘marine lakes’’ are known to occur on the Raja Ampat Islands of Mansuar and Misool. The pool on Mansuar is surrounded by mangrove and rain-forest, has a soft silty bottom, a narrow band of algae and sponge along the perimeter. Five fish species are present in this ecosystem, including Kalyptatherina helodes, the only member of the family Telmatherinidae known outside of Sulawesi. This same fish species is also found in clear waters of sheltered mangrove-coral reef inlets throughout the Raja Ampat Islands.

      On the islands adjacent to the Papuan region (e.g., Timor), anchialine pools occur primarily in elevated fossil reef rock, and are variable in depth depending on tidal stage, with certain very shallow pools appearing only at high tide. Their surface waters are generally mixohaline, ranging from 1–10 o/oo, but occasionally approach euhaline levels, and are usually clear and circumneutral, with temperatures ranging from 22–30 C. Waters within individual pools are usually homioha-line, but with sharp, stable, vertical salinity stratification evident in deeper pools. Although there are no direct surface connections with ocean, tidal fluctuations are also usually still evident, because the water surface level is merely an inland extension of the marine water table, with the mixohalinity resulting from dilution of intruding ocean water with seaward-percolating groundwater. Such pools may occur singly, but are more typically found in groups with subsurface interconnections, and thus represent surface manifestations of otherwise subterranean ecosystems.

      The biota of anchialine pools is unique and distinctive, with some faunal species, particularly red shrimps, not found elsewhere. Introduction of alien fishes quickly degrades or eliminates such crustacean communities, a process well documented elsewhere in the Pacific, particularly Hawai’i.

      Subterranean Aquatic Ecosystems

      The anchialine pools discussed in the preceding section are localized surface exposures of larger and more extensive subterranean aquatic ecosystems that occur in all areas of tropical karst terrain. Such ecosystems may be lotic, such as the ‘‘Baliem Swallet,’’ where the Baliem River disappears underground for a considerable distance near Mt Trikora, or lentic, in the form of standing pools within cave systems. Despite the known existence of such ecosystems in Papua, their faunal exploration has been extremely limited. Cursory collections