Plantation Streams Research Articles

Aquatic insect communities in headwater streams of Ciliwung River watershed, West Java, Indonesia

Abstract. Wakhid, Rauf A, Krisanti M, Sumertajaya IM, Maryana N. 2021. Aquatic insect communities in headwater streams of Ciliwung River watershed, West Java, Indonesia. Biodiversitas 22: 30-41. Ciliwung is one of the major rivers flowing from Cisarua (Bogor) to Jakarta. This study was conducted to assess and compare aquatic insect biodiversity and community structure in various headwater streams with respect to different land-use types. Ten stream reaches of the first and second orders representing three different land-use types in the surrounding area (forest, tea plantation, village) were selected. At each stream reach, the aquatic insects were collected using a D-net (0.4 mm mesh). Physico-chemical properties of water were directly measured in the field. Samples were collected every two months from April until December 2018. A total of 26531 aquatic insect specimens belonging to 75 species/morphospecies, 46 families, and 10 orders were recorded. The order Trichoptera was the most abundant comprising 51.28% of the total collected insects, followed by Diptera (30.5%), Ephemeroptera (7.52%), and Plecoptera (6.25%). The highest proportion of functional feeding group was filtering-collectors (61.34%), followed by shredders (16.29%), gathering-collectors (15.32%), and predators (6.94%). Abundance of Diptera and Plecoptera was significantly higher in forest streams, while Ephemeroptera in plantation streams, and Trichoptera in village streams. The peak population of Diptera, Ephemeroptera, and Trichoptera occurred in June (dry period), while Plecoptera in December (wet period). The forest streams exhibited the highest species richness and diversity. Analysis of similarity (ANOSIM) showed a low dissimilarity among streams of the three land uses (Global R=0.217; P<0.001). The non-metric multidimensional scaling (NMDS) analysis showed that forest streams somewhat separated from plantation and village streams. The study provided important information on aquatic insect biodiversity, and indicated the need for forest area preservation in the headwater streams of Ciliwung River watershed.

Forest conversion to oil palm compresses food chain length in tropical streams.

In Southeast Asia, biodiversity-rich forests are being extensively logged and converted to oil palm monocultures. Although the impacts of these changes on biodiversity are largely well documented, we know addition to samples we collected in 201 little about how these large-scale impacts affect freshwater trophic ecology. We used stable isotope analyses (SIA) to determine the impacts of land-use changes on the relative contribution of allochthonous and autochthonous basal resources in 19 stream food webs. We also applied compound-specific SIA and bulk-SIA to determine the trophic position of fish apex predators and meso-predators (invertivores and omnivores). There was no difference in the contribution of autochthonous resources in either consumer group (70-82%) among streams with different land-use type. There was no change in trophic position for meso-predators, but trophic position decreased significantly for apex predators in oil palm plantation streams compared to forest streams. This change in maximum food chain length was due to turnover in identity of the apex predator among land-use types. Disruption of aquatic trophic ecology, through reduction in food chain length and shift in basal resources, may cause significant changes in biodiversity as well as ecosystem functions and services. Understanding this change can help develop more focused priorities for mediating the negative impacts of human activities on freshwater ecosystems.

Is eating wild rainbow trout safe? The effects of different land-uses on heavy metals content in Chile

Cu, Mn, Fe, Zn, Cd and Pb levels were measured in liver and muscle samples of Rainbow Trout Oncorhynchus mykiss collected from three watersheds with different land-uses: native forest, exotic plantation, and agriculture in Chile, during January, April, July, and October 2012. Cd and Pb levels were not detected in the liver and muscle, probably since they are under the detection limits. Higher metal concentrations (liver-muscle tissues) were detected in samples from agriculture and exotic plantation streams, whereas trout from native forest streams had lower metal concentrations. Higher metal concentrations were detected in liver tissue compared to muscle tissue, and both negatively correlated to the length and weight of the fish. This suggest the liver had higher ability to accumulate Cu, Mn, Fe and Zn compared to muscle tissue. The concentration range of Fe and Zn recorded in the muscle are within the range reported by other authors, whereas Mn and Cu concentrations are higher than reported in the literature. However, at all sites the concentration of selected metals were below the limits permitted by current legislation (FAO), and therefore did not put the human population at risk, suggesting that is eating wild rainbow trout safe in Chile.

Response of benthic invertebrate communities to a land use gradient in tropical highland streams in Nigeria

Benthic invertebrate communities have been shown to respond to habitat degradation as a result of land use changes. Although these changes have been well documented in temperate regions, their effects in the tropics have been poorly documented particularly where land use activities differ markedly (e.g., tea, maize and plantations). A survey 55 1st and 2nd order highland tropical streams, across four land use categories, ranging from continuous tropical montane rain forest to intensive crops and pasture. Streams were sampled in the tropical dry season (October–March) for physico-chemical parameters and components of the biological community, (i.e., fine particulate organic matter [FPOM], coarse particulate organic matter [CPOM], algae and benthic invertebrates). Catchment riparian conditions and human water use activities were used to generate a multivariate land use intensity gradient score. Temperatures in pasture streams were warmer than forest streams (up to 25oC) and dissolved oxygen levels frequently low (15–79%). However, physico-chemical conditions did not show any clear patterns across land uses categories. In contrast, benthic invertebrate communities showed strong response with the highest taxonomic diversity in continuous forest streams (mean 20 taxa) and the lowest in streams with intensive crops (e.g., cabbage crops, mean 8 taxa). Marked changes were found in invertebrate communities with several taxa occurring primarily in forested streams (e.g., the mayflies Heptageniidae and Oligoneuriidae and brachyuran crabs). Tropical land use farming (e.g., tea, maize, cabbage) have significant impacts on the benthic invertebrate assemblages of highland streams in Nigeria. However, not all crop and plantation streams had highly impacted communities because some have wider riparian buffer zones. This study further highlight the importance of conservation and management of montane forest fragments in these regionsKeywords: Tropical, Nigeria, highland, benthic invertebrates, land use, degradation

Effects of oil palm plantations on habitat structure and fish assemblages in Amazon streams

The aim of this research is to assess the effects of oil palm plantations on stream habitat and their fish assemblage diversity. We hypothesize that streams which drain through oil palm plantations tend to be less heterogeneous, limiting the occurrence of many species, than streams that drain through forest fragments, which support higher fish diversity. A total of 17 streams were sampled; eight in forest fragments and nine in oil palm plantations. Environmental and biological variables were sampled along 150 m stretch in each stream. Of the 242 environmental variables measured, ten were considered important to assess the condition of structural habitat, and out of these variables, four were considered relevant in the distinction between streams in oil palm plantations and forest fragments. A total of 7245 fishes were collected, belonging to 63 species. Unlike our original hypothesis, the species richness did not differ between forest fragment and oil palm plantations streams, showing that it is not a good divert measure in streams disturbance assessment. However, fish assemblages differed in species composition, and 56 species were recorded in oil palm plantation streams, while 44 species were recorded in forest fragments streams. Some species were identified as indicators of either altered (Aequidens tetramerus and Apistogramma agassizii) or undisturbed areas (Helogenes marmoratus). Overall, oil palm plantations were proven to change stream habitat structure and fish species distribution, corroborating other studies that have evidenced changes in patterns of biological community structure due to impacts by different land uses.

Influence of oil palm monoculture on the taxonomic and functional composition of aquatic insect communities in eastern Brazilian Amazonia

Large scale palm oil plantations for the production of vegetable oil are among the most harmful agricultural activities to biodiversity, especially given their rapid expansion, worldwide. Many cases of species loss have already been recorded in Asian countries, although research is still incipient in the Amazon basin, and the environmental impacts of these monocultures on freshwater ecosystems in the Neotropical region are still poorly understood. The present study evaluated the effects of oil palm plantations on the physical structure of stream habitats and the resulting changes in the taxonomic and functional composition of aquatic insect communities. A total of 2100 specimens of the orders Ephemeroptera, Plecoptera and Trichoptera were collected during the present study, representing 40 genera and 16 families. The hypothesis tested was that the taxonomic and functional diversity of the orders Ephemeroptera, Plecoptera and Trichoptera (Insecta) decreases in streams surrounded by oil palm plantations in comparison with those embedded in forested areas. In the plantation streams, the taxonomic richness and composition, and the functional richness are modified significantly. Functional composition appeared unaltered despite reduced canopy cover associated with oil palm streams. These effects emphasize the importance of the riparian vegetation for the protection of the aquatic communities found in oil palm plantations. The maintenance of the riparian vegetation may mitigate the impacts of plantations, contributing to the conservation of insect communities and associated biodiversity.

Effects of land use on larval Odonata assemblages in cloud forest streams in central Veracruz, Mexico

This study analyzes the effect of stream water quality and its relationship with habitat characteristics on larval Odonata assemblages in streams found in tropical montane cloud forests, pastures, and coffee plantations in the upper La Antigua River watershed. The main factors that influenced larval Odonata assemblages in forest streams were low temperatures and high oxygen levels in water, coupled with a high diversity of the substrate and riparian vegetation; in pasture streams and coffee plantation streams, sedimentation strongly affected the composition of larval Odonata assemblages. In all the streams, species richness (0D) was higher during the dry season. The highest Shannon α diversity (1D) values were found in forest streams during the rainy season; however, in pasture and coffee plantation streams, 1D values were higher during the dry season. The low species turnover in forest streams suggests that these streams provide highly stable conditions for Odonata assemblages; however, in pasture and coffee plantation streams, the higher turnover was related to the more variable water and habitat conditions. Thus, the persistence of Odonata assemblages in the upper La Antigua River watershed is closely related to the conservation status of the tropical montane cloud forests.

Effects of Logging and Oil Palm Expansion on Stream Frog Communities on Borneo, Southeast Asia

AbstractThe conversion of tropical rain forests to oil palm plantations is a major threat to Southeast Asia's rich biodiversity. Fostering forest species communities in secondary forests, agroforestry systems, and plantations is therefore increasingly becoming a conservation focus. This study uses standardized transect‐based sampling to compare species richness, density and community composition of stream anuran assemblages among primary forests, repeatedly logged forests and oil palm plantations in northern Borneo. In primary forest streams, we recorded an average of 19 frog species, compared to 15 species in logged forests and 11 species in oil palm plantation streams. However, the high percentage of canopy cover above the plantation streams mitigated this loss to some extent. This study corroborates numerous studies that oil palm plantations have mainly negative effects on the region's biodiversity. However, our results also demonstrate the high conservation value of logged forests for Bornean stream‐dependent anurans. We conclude that palm plantations have a largely unused potential to promote regional anuran biodiversity.

Mitigating the impact of oil-palm monoculture on freshwater fishes in Southeast Asia.

Anthropogenic land-cover change is driving biodiversity loss worldwide. At the epicenter of this crisis lies Southeast Asia, where biodiversity-rich forests are being converted to oil-palm monocultures. As demand for palm oil increases, there is an urgent need to find strategies that maintain biodiversity in plantations. Previous studies found that retaining forest patches within plantations benefited some terrestrial taxa but not others. However, no study has focused on aquatic taxa such as fishes, despite their importance to human well-being. We assessed the efficacy of forested riparian reserves in conserving freshwater fish biodiversity in oil-palm monoculture by sampling stream fish communities in an oil-palm plantation in Central Kalimantan, Indonesia. Forested riparian reserves maintained preconversion local fish species richness and functional diversity. In contrast, local and total species richness, biomass, and functional diversity declined markedly in streams without riparian reserves. Mechanistically, riparian reserves appeared to increase local species richness by increasing leaf litter cover and maintaining coarse substrate. The loss of fishes specializing in leaf litter and coarse substrate decreased functional diversity and altered community composition in oil-palm plantation streams that lacked riparian reserves. Thus, a land-sharing strategy that incorporates the retention of forested riparian reserves may maintain the ecological integrity of fish communities in oil-palm plantations. We urge policy makers and growers to make retention of riparian reserves in oil-palm plantations standard practice, and we encourage palm-oil purchasers to source only palm oil from plantations that employ this practice.

Oil palm crops effects on environmental integrity of Amazonian streams and Heteropteran (Hemiptera) species diversity

Climatic and edaphic conditions in the Amazon basin are ideal for the cultivation of the oil palm (Elaeis guineensis Jacq.), this has led to a major expansion in plantations in recent years, to the point where oil palm cultivation has become one of the main threats to biodiversity in this biome. This study aimed to evaluate the effects of oil palm crops on the integrity of freshwater environments and assess the response of aquatic assemblages. A set of 244 environmental metrics were measured at 22 Amazonian streams, either reference sites located in natural forest or oil palm plantation sites. We developed an aquatic environment integrity index for these sites. Biological sampling consisted of the collection of specimens of aquatic and semi-aquatic Heteropteran species. From environmental variables dataset, some were evaluated and five were screened to assess the environments and employed in the streams abiotic integrity index (SAII) to these environments. The SAII proved an excellent for assessing aquatic environments and assaying changes in the freshwater habitats (forest and oil palm) analysed in this study. The forest streams had higher environmental integrity than the plantation streams. Environmental integrity was associated with Heteropteran species richness, although not to abundance of individual species. These results are consistent with previous research on the effects of oil palm crops on aquatic habitats, which showed that the greatest impact was on factors associated with the structure of the riparian zone. These findings should inform development of a strategy to mitigate or minimise the environmental problems caused by ongoing expansion of oil palm plantations in the Amazon basin, in order to safeguard the region's aquatic biodiversity.

Are aquatic insect species sensitive to banana plant cultivation?

Ephemeroptera, Plecoptera, Trichoptera and Coleoptera (EPTC) insect fauna were collected in ten streams located in the southeastern state of São Paulo (five located in areas with banana cultivation and five located in preserved areas). Specimens were collected during October and November 2005, using a Surber sampler and network D (0.25mm mesh size) in areas of rapids and backwaters. The organisms collected were identified to genus level, except for some small or damaged specimens that remained at the family level. In total, 1812 individuals of EPTC were identified, in which 1105 organisms were from streams in areas of banana cultivation and 706 from streams in preserved areas. Heterelmis (Elmidae) was dominant in both sets of streams. In preserved streams, Hexacylloepus (Elmidae), Tupiperla and Paragrypopteryx (Gripopterygidae) and Nectopsyche (Leptoceridae) also had high participation. Leptonema (Hydropsychidae) and Xenelmis (Elmidae) were dominant in streams located in areas of banana cultivation. The analyses of indicator species point out to five taxa on preserved streams and two taxa in the banana streams. The forested streams had higher richness and diversity of EPTC than banana plantation streams. Correspondence analysis point for two groups, one gathered in the streams near the banana plantation and the other in the preserved streams. The similarity test (ANOSIM) pointed to significant differences (P<0.05) between these groups. This agricultural activity seems to influence the EPTC community structure in low order streams in the Atlantic Forest region. The identification of groups at the EPTC genus level was important to point out the differences between the fauna of streams impacted by banana cultivation and to establish indicator species.

Relationship between banana plant cultivation and stream macroinvertebrate communities

AIMS: The present study describes the influence of banana plant cultivation on macroinvertebrate communities of streams located in the southeastern region of São Paulo state in the Atlantic Forest (four located in areas of banana cultivation and four in preserved areas); METHODS: Sampling was performed during October and November of 2005. The fauna was collected with Surber sampler and a D-aquatic net (both with mesh of 0.25 mm) in rapids and backwaters. Simultaneously, an environmental characterization of each stream was made; RESULTS: In total, 3,609 individuals were collected, distributed in 57 families, in which 45 were in forested streams and 46 in the banana plantation sites. Gripopterygidae, Perlidae, Leptophlebiidae, Leptoceridae, Helicopsychidae and Palaemonidae were abundant in forested streams, while Hydropsychidae, Chironomidae and Baetidae were abundant in the streams located in banana cultivation areas. Cluster analysis (UPGMA) with Simpson similarity measurement applied to the fauna of all streams evidenced the differences between forested and banana plantation streams. An analysis of similarity applied to both situations also pointed to significant differences (p &lt; 0.05) between the two areas; CONCLUSIONS: This agricultural activity, although did not influence species richness patterns, seems to influence the structure of macroinvertebrate communities in low order streams in the Atlantic Forest region.

Breakdown and macroinvertebrate colonization of needle and leaf litter in conifer plantation streams in Shikoku, southwestern Japan

Breakdown and macroinvertebrate colonization of conifer needles (Cryptomeria japonica) and deciduous broadleaves (Euptelea polyandra) were investigated using litter bags in two study sites in streams flowing through a conifer plantation of C. japonica in Shikoku, southwestern Japan (one site with conifer canopy and another with mixed conifer and broadleaved canopy). Breakdown rates and macroinvertebrate densities were compared between litter species (conifer needle vs broadleaf) and between the two sites (conifer vs mixed canopy) to determine (1) whether breakdown rate of broadleaves is higher than conifer needles, (2) whether macroinvertebrates prefer broadleaves to conifer needles, and (3) whether the difference in riparian canopy is reflected in macroinvertebrate abundance. The results indicated that breakdown rates of broadleaves were higher than those of conifer needles, suggesting poorer quality of the latter as food for macroinvertebrates. Differences in macroinvertebrate density between needles and broadleaves were generally consistent with those in breakdown rates: broadleaves tended to have higher densities than needles, suggesting that conifer needles were not preferred by macroinvertebrates. However, total macroinvertebrate density in the conifer site was not significantly different from that in the mixed site, although the dominant shredder taxon differed (conifer site: gammarids; mixed site: lepidostomatids). Although conifer needles are low-quality food for macroinvertebrates, this may offer some advantages. Conifer needles remain on the streambed for longer periods owing to their lower breakdown rates, being a constantly available resource. In addition, accumulations of conifer litter may effectively trap and retain particulate organic matter.

Invertebrate community structure and ecosystem functioning in European conifer plantation streams

Summary1. Terrestrial leaf‐litter is the dominant energy input to many headwater streams and consequently the nature of the riparian vegetation can have profound effects on in‐stream processes. The impact of conifer plantations on community structure and ecosystem functioning (litter breakdown) was investigated in field experiments in three countries (Britain, Ireland, Poland), each representing a distinct European ecoregion. Twenty‐six streams were used in the trial: half were bordered with broadleaved and the other half with conifer riparian vegetation.2. In a leaf breakdown study using litter bags, two leaf types (oak and alder) were used to assess the impact of resource quality and two mesh sizes (10 and 0.5 mm aperture) were used to gauge the relative importance of invertebrate detritivores and microbial decomposers respectively. Comparisons were made between vegetation types and among regions; pH varied among individual streams but, unlike many previous studies, it was not confounded with vegetation type, enabling us to isolate the effect of vegetation more effectively.3. Overall, riparian vegetation type did not affect breakdown rates but strong regional differences were observed. There was also a significant interaction between these two variables, but this disappeared after fitting pH as a covariable, demonstrating its importance in determining breakdown rates and raising the possibility that in previous studies the impacts of conifer plantations might have been confounded with pH.4. Shredder species composition differed between vegetation types. Small stoneflies were most strongly associated with conifer streams; broadleaved streams generally had a higher proportion of larger taxa, such as limnephilid caddisflies and gammarid shrimps, although the latter were excluded from sites with low pH. However, breakdown rates were maintained irrespective of shredder community composition, suggesting a high degree of functional redundancy in these communities. Similar processing rates were observed between streams with high numbers of nemourids and those with only a few limnephilids or gammarids, suggesting that density compensation among consumers might stabilise process rates.5. Our results suggest that leaf‐litter breakdown can be an effective proxy for assessing stream ecosystem functioning, as rates differed significantly across spatial scales, from between streams to across regions and responded to an environmental gradient (pH). The litter bag technique can also complement traditional assessment methods by providing valuable information on the composition of consumer guilds, thereby providing an important link between structure and function that is needed to help inform management practices.

Leaf transport and retention in a high gradient stream

Abstract. To a large extent, the invertebrate fauna in wooded streams rely upon detritus inputs from the surrounding vegetation as their main food source. Conifer plantations may alter the timing and nutritional quality of leaf inputs into streams, but detritus retention may also be reduced. While it has often been assumed that conifer needles are retained less than broadleaved species, this has never been tested experimentally. This study describes the results of a leaf release experiment carried out in a small headwater stream, comparing the retention of pine needles and oak leaves (wet and dry) over a range of discharges. In addition, retention was compared before and after placing logs in the stream to examine the effect of woody debris on retention efficiency. Retention efficiency was significantly different among the three leaf types tested with wet oak leaves being most retentive, followed by dry oak leaves with dry pine needles being least retentive. Retention efficiency declined significantly with increasing discharge for all three leaf types. The addition of logs increased the retention of dry oak leaves and pine needles, but not wet oak leaves. The predominant features (stones, logs, eddies and bankside vegetation) that accounted for retention varied with discharge and the leaf type used. The results indicate that while conifer needles may be inherently less retentive than broadleaves, the presence of woody debris within the stream channel increases their retention. However, this small-scale study would need to be expanded to investigate the retention dynamics of conifer needles in plantation streams. Nevertheless, management strategies that allow the formation of woody debris accumulations in plantation streams could be valuable in enhancing detritus retention and consequently could benefit invertebrate communities. Keywords: pine needles, retention efficiency, woody debris, discharge

The response of macroinvertebrates to artificially enhanced detritus levels in plantation streams

Abstract. The leaves and wood from vegetation surrounding headwater streams constitute a major food source for aquatic invertebrates, providing they are retained upon the streambed and not transported downstream. This study investigated the response of aquatic invertebrates to artificially increased detritus retention, in an effort to reproduce the naturally occurring build up of dead organic matter associated with streams in old-growth forest. The background detrital standing stock in streams in Kielder Forest (Northumberland, UK) was low, approximately 32 gm-2. Two streams flowing through dense conifer plantation and one in open broadleaved woodland were manipulated by the addition of logs over a 10 m stream reach. After several months, log addition significantly enhanced detrital standing stocks in both conifer and broadleaved streams. Total invertebrate abundance, taxon richness and the numbers of certain numerically dominant families were significantly higher in experimental than reference reaches in both conifer and broadleaved streams. This response was most marked for detritivores, whilst non-detritivore groups often showed no response to the manipulation. Whilst in the short term the responses to enhanced retention may reflect a redistribution of the local fauna, it is argued that over a longer time-scale, a genuine increase in invertebrate density and diversity could occur. Allowing old-growth forest to develop in planted valley bottoms may be a viable management option for conservation. If established alongside streams, it would ensure continuous input of woody material and the fauna may benefit from the resulting increase in detritus retention. Keywords: forestry, detritivores, old-growth conifers, river management, woody debris

Influence of large woody debris on channel morphology in native forest and pine plantation streams in the Nelson region, New Zealand

The influence of large woody debris (LWD) on channel morphology was assessed in five pine plantation and five native forest streams in the Nelson region of New Zealand. LWD volumes averaged 127 m3 ha–1 in pine plantation streams and 94 m3 ha–1 in native forest streams. Most of the LWD in pine and native streams had no influence on channel morphology (78 and 54%, respectively). Those LWD pieces influencing channel morphology contributed mainly to sediment storage in both pine and native streams as well as flow deflection and debris collection in the native streams. Wood aligned either perpendicular or obliquely to stream flow and positioned on or partly buried in the stream bed had the greatest influence on channel morphology. There were twice as many pools in native streams as in pine streams, and scour processes formed the majority of pools. LWD influenced c. 50% of pool formation in both pine and native streams and increased pool variety. LWD volumes in these streams are low compared with Pacific north‐west streams of the United States, similar to streams in the subalpine forest of Colorado, and higher than volumes in the more modified streams of Europe. Similarities in pool forming processes, pool type, and spatial arrangement of wood influencing channel morphology are apparent between the streams in this study and streams of the Pacific north‐west and Colorado.

Response of aquatic hyphomycete communities to enhanced stream retention in areas impacted by commercial forestry

1. Aquatic hyphomycetes are an important component of detritus processing in streams. Their response to enhanced stream retentiveness was tested by manipulating three streams located in Kielder Forest (northern England), a large plantation of exotic conifers, and two streams in Montagne Noire (south‐west France) dominated by native broadleaf woodland. Treatment was by placement of logs or plastic litter traps into a 10–20 m stream section. Fungal spores were collected from stream water upstream and downstream of the treated sections over 1–2 years.2. The average concentration of fungal spores in reference sections was nearly 10× greater in the French streams than in the English streams. The number of hyphomycete species was also higher in the French streams. These differences between regions were probably a consequence of the much lower standing stock and diversity of leaf litter in the English streams.3. Despite these large regional differences, the treatment had a clear effect in all streams. Detrital standing stocks were enhanced in treated sections by up to 90% in French streams and 70% in English streams.4. Mean spore density below treated sections increased by 1.8–14.8% in French streams and 10.2–28.9% in the naturally less retentive English streams. The number of fungal species increased significantly below the treated sections of the English streams, although not the French ones.5. In biologically impoverished plantation streams, input of woody debris can increase detritus retention and enhance hyphomycete diversity and productivity. This may have consequent benefits for detritus processing and macroinvertebrate production.