On the little-known hyporheic biodiversity of India , with annotated checklist of copepods and bathynellaceans ( Crustacea ) and a note on the disastrous implications of indiscriminate sand mining

Acknowledgements: The author is grateful to the authorities of Acharya Nagarjuna University for extending necessary facilities. The author also expresses his grateful thanks to the anonymous reviewers for providing several critical comments. Abstract: The vast and ecologically diversified hyporheic realm and the adjacent riparian areas of India have received scant attention from the standpoint of biodiversity studies. Analysis of about 2500 samples collected from the alluvial sediments of certain rivers and streams, besides some bores in the riparian zone, mainly in the coastal deltaic belt of the rivers Krishna and Godavari in Andhra Pradesh State during 2000–2012 yielded 41 copepod and bathynellacean species. Of these, 31 new species have been formally described during the ongoing studies whereas the remainder are previously known ones. An annotated checklist of all these taxa is presented, giving the type locality and other localities of occurrence, methods of sampling, chief references, and also some taxonomic and/or ecological remarks wherever necessary. The harpacticoid copepod family Parastenocarididae and the eumalacostracan order Bathynellacea are two significant, major groups of stygofauna that have been recorded for the first time from India. Both these groups and also some cyclopoid copepods have clear-cut Gondwanan lineages, representing the remnants of unique ancient fauna that require urgent attention from conservationists in order that the overall evolutionary history of the Indian biota is preserved. A note is also added on the devastating influence of the ongoing rampant sand mining activity on the hyporheic biodiversity.


INTRODUCTION
To save the earth's fast-depleting biodiversity, which is due primarily to habitat loss and impairment, has become a matter of increasing concern for scientists and governments all over the world.What is even more disconcerting today is that certain unique and asyet unexplored habitats are imperiled even before the study of their biodiversity and functions has begun in right earnest.One such greatly threatened habitat is the hyporheic habitat present within the sandy banks of rivers and streams.In India, scant attention, if any, has been paid to the study of hyporheic ecosystems.This paper gives, after briefly referring to the general biodiversity and functions of the hyporheic zone, an annotated checklist of the hyporheic copepod and bathynellacean crustaceans (size c. 1mm).This checklist is based on the taxonomic and biogeographic studies carried out during the last decade or so, mostly in the coastal deltaic belt of the rivers Krishna and Godavari in Andhra Pradesh State.Stringent legislative measures are suggested for protecting these precious sanddwellers and their home, now under the devastating impact of excessive sand extraction.Incidentally, the stray hypogean copepod and bathynellacean species encountered in the riparian bores and two caves are also included in the checklist.
The term hyporheic, derived from Greek rootshypo, meaning under or beneath, and rheos, meaning a stream, was first used by the Romanian hydrologist Orghidan (1959).It originally refers to the alluvial sediments that extend vertically and laterally from the river channel, giving rise to 'a rich and unique ecosystem'.Demonstrating the double influence of groundwater and stream properties on this ecosystem, Orghidan distinguished it from other groundwater habitats.And the subsequent pioneering work by Stanford & Ward (1993) proposes to integrate the stream channel and hyporheic systems into a river continuum conceptthe hyporheic corridor.Essentially, the hyporheic zone constitutes 'a spatially and temporally dynamic ecotone' (Feris et al. 2003), sandwiched between the surface water and groundwater ecosystems.This 'critical interface' extends from the substrate surface to a depth of about 50cm, below which lies the phreatic or groundwater regime (Pennak 1940).Its functional role is governed by such properties as its elasticity, permeability, biodiversity, and connectivity (Gibert et al. 1990;Vervier et al. 1992) in close interaction with the geomorphology, geohydrology, landscape use and the buffering ecosystems along the river corridor.It is in this zone that hydrological, ecological and biogeochemical processes interact, influencing key ecosystem processes such as primary productivity and nutrient cycling (Mulholland & Webster 2010).Hence, the findings concerning the functional significance of the hyporheic zone are of crucial importance in floodplain management and restoration (Boulton et al. 2010).Overall, the hyporheic science, which is a vital facet of groundwater ecology and 'a topic of great practical relevance' to regulators and policy makers, has been recognized in the West as a fascinating, multidisciplinary field that combines methods, concepts and data from hydrogeology, geochemistry, microbiology and aquatic ecology (Larned 2012).Besides being the home of rich biodiversity, the hyporheic zone endows us with a number of 'ecological goods and services' such as the following: offers a spawning ground and refuge for certain fishes (salmon, etc.) and rooting zone for aquatic plants; controls the flux and location of water exchange between streams and subsurface; acts as a buffer zone for the attenuation of certain pollutants by biodegradation, sorption and mixing; provides an important zone for biogeochemical cycling of carbon, energy and nutrients; forms a functional sink/source for fine organic detritus and other sediments; and moderates water temperature against heat and freezing (Environment Agency 2009).

MATERIALS AND METHODS
About 2500 core samples collected mainly from the alluvial sediments mostly in the coastal deltaic belt of the rivers Krishna and Godavari and also from the riparian/ phreatic bores in Andhra Pradesh State (exceptions: only a single sample each from the river Sutlej in Himachal Pradesh State and River Muvattupuzha in Kerala State, and two samples from cave pools) during 2000-2012 by adopting the following methods: (1) Karaman & Chappuis method (Chappuis 1942): This method, the most frequently used one, entails digging a few holes of varying depths (10-30 cm) a few meters apart from one another in the alluvial deposits next to a stream or river, and sampling the subsurface water seeping into the pits.Each time the sample was filtered through bolting-silk plankton net (mesh size 70μm), and the filtrate fixed in 5% formaldehyde in plastic vials.
(2) Coring and filtration method: A rigid PVC tube (length c. 70cm, diameter c. 10cm) was used to extract cores from the sediment surface to a depth of 10-50 cm from both exposed and submerged parts of stream/river banks.At each site, the core samples were pooled in a bucket, filled with the water from the sampling spot and stirred vigorously.The supernatant was filtered and fixed as mentioned above.
(3) Direct filtration of water from farm bores in the riparian zone: Specimens were collected by filtering the water when it was pumped out of farm bores (depth c. 10m) adjacent to rivers.Filtering was done manually by holding a bolting-silk plankton net (mesh size 70µm) against the water current for 20-30 minutes at each time of sampling.The filtrate was fixed as before.

Phylum
Sampling method: Coring and filtration method.
Other localities: None.Sampling methods: Karaman & Chappuis method and Coring and filtration method.

DISCUSSION
In India, both the Himalayan and Peninsular River Systems present vast and ecologically diversified hyporheic realm and riparian areas, apparently harboring enormous biodiversity.However, as already mentioned in the Introduction, little is known about the Indian hyporheic biota.This is due to the minute size of most of the organisms, the difficulties involved in their sampling, the exacting microscopic study and drawing work, the lack of taxonomic expertise and funding support, etc.
The present faunistic survey covering only a fraction of the Indian hyporheic and riparian realm is indeed rewarding in that it has yielded 41 copepod and bathynellacean species, of which as many as 31 species are new to science and formally described and the remaining one are previously known in the literature; an additional 20 new species in the samples are yet to be named and described.The eumalacostracan order Bathynellacea and the harpacticoid copepod family Parastenocarididae are two significant, major groups of stygofauna that have been recorded for the first time from India.Both these groups are of much value in historical biogeography and phylogenetic studies.In particular, the Bathynellacea represents one of the oldest freshwater crustacean groups whose ancestors inhabited the seas in the Carboniferous or even earlier, now absent from the epigean realm.This group as a whole might have achieved its worldwide distribution prior to the breakup of Pangaea, and its present biogeography can be more convincingly explained by the vicariance model rather than by the classical dispersal model (Schminke 1974;Schram 1977Schram , 2008)).It is noteworthy that while all the Indian bathynellacean taxa are distinctly different from their Asian counterparts, they display spectacular Gondwanan heritage (Ranga Reddy 2011b).Of the two Indian endemic genera Serbanibathynella and Indobathynella, the latter is the most derived one in the family Bathynellidae.The parabathynellid genus Habrobathynella is remarkably speciose with as many as 12 Indian species (three new species present in the samples are yet to be named and described), nine of them inhabiting the sandy sediments of peninsular rivers.This genus is known outside India only by two species in Madagascar.
According to Noodt (1969), compared with the Bathynellacea, the Parastenocarididae is a much younger group, having originated possibly in the early Tertiary or even earlier.However, because parastenocaridids have no marine relatives or modern pathways between different continents (Boxshall & Jaume 2000), it has been postulated that they have a Pangaean origin (Karanovic 2006).The latter taxon is as yet known by 11 species in India.While eight species are distributed in alluvial sediments, one species each is restricted to a cave and two to riparian borewells.Two genera, viz., Kinnecaris and Siolicaris, have distinct Gondwanan affinities and so do three cyclopoid copepod genera, viz., Haplocyclops, Rybocyclops and Allocyclopina as well (Ranga Reddy 2011b).Since the Gondwanan lineages represent the remnants of unique ancient biota (Mani 1974;Roelants et al. 2004), they require urgent attention from conservationists in order that the overall evolutionary history of Indian biota is preserved (Karanth 2006).All in all, these tiny ancient crustaceans inhabiting the sandy sediments are no less important than the spectacular epigean vertebrates in understanding the evolutionary history of the earth's crust.
It is also worthy of note that amongst the other harpacticoid copepod species, Delavalia madrasensis, Folioquinpes chathamensis, Neomiscegenus indicus, and Mesochra wolskii belong to the almost exclusively marine families.Clearly, the occurrence of these species in the truly freshwater conditions of the hyporheic zone of the river Krishna near Vijayawada is indicative of their remarkable euryhaline adaptations.

CONSERVATION
Construction boom in the wake of rapid urbanization has fuelled increasing demand for river sand.As a result, all the Indian rivers without exception have been and are still literally plundered of their alluvium on a large scale.Sand miners are digging to a depth of about 15m with the help of machines, and even extracting the earth after touching the river floor.Besides the staggering and visible on-site and off-site ill-effects of uncontrolled sand extraction such as channel degradation and erosion, deepening of rivers and enlargement of river mouths, lowering of water tables in the nearby riparian areas plus occasional saline-water intrusion from the nearby seas, infrastructure damage like undermining of bridges and other structures, etc. (see Kondolf & Swanson 1993;Kondolf 1997;Mori et al. 2011), and sadly and more importantly, the highly fragile hyporheic habitats and their associated biota are gouged out along with their homes, as it were.In this connection, it is also noteworthy that the dubious 'eco-friendly' policy announced by certain state governments, providing for sand extraction up to 2m, is utterly myopic and disastrous to sand-associated life because most of the hyporheic life is confined to the upper one meter or so of the sediment.This fact must be taken cognizance of by the policy makers.
Considering the ecological importance of the hyporheic biodiversity in riverine ecosystem functioning, total ban must be imposed on sand mining activities.Should this be not feasible, at least certain tracts of each of our river banks must be given legal protection against the sand mafia so that such protected corridors could ensure the regeneration and preservation of the hyporheic biota.Simultaneously, immediate steps need be taken to encourage research activities leading to the finding of suitable, low-cost and easily available alternatives to river sand for construction industry.In view of the importance of hyporheic science as a multidisciplinary area of specialization, funding agencies in the country will do well to play a pro-active role in encouraging research in this area, starting from the taxonomic characterization of species.