Effects of novel, non-native detritus on decomposition and invertebrate community assemblage

When non-native primary producers become successful, the structure and function of native detrital food webs can be fundamentally altered. Salt marsh estuaries of the southeastern USA are in part detritus-based ecosystems and rely on the annual production of detritus from a single native species, the smooth cordgrass Spartina alterniflora. Over the last several decades, the success of a novel primary producer, the red macroalga Agarophyton vermiculophyllum (formerly Gracilaria vermiculophylla), in a system historically devoid of macroalgae provides the opportunity to measure the effect of non-native basal resources on native detrital pathways. We conducted 2 in situ experiments to compare (1) decomposition rates of A. vermiculophyllum and S. alterniflora and (2) invertebrate colonization rates onto dead A. vermiculophyllum and S. alterniflora. Relative to S. alterniflora, we found that A. vermiculophyllum decomposes more rapidly, losing 80% or more of its biomass within 3 wk, while S. alterniflora lost ~50%. Experimental litterbags with decomposed A. vermiculophyllum and S. alterniflora harbored similar highly abundant invertebrate communities that differed greatly from denuded areas. Our results demonstrate that A. vermiculophyllum provides a complementary source of labile organic matter relative to S. alterniflora, boosting the amount of food and available habitat for small invertebrates of intertidal salt marshes and mudflats. Thus, non-native macrophytes may differentially affect community and ecosystem properties just as much when dead as alive, especially when they are biologically distinct from native species.

Rolling stones gather moss: Movement and longevity of moss balls on an Alaskan glacier

Glaciers support diverse ecosystems that are largely comprised of microbial life. However, at larger, macroscopic scales, glacier moss balls (sometimes called “glacier mice”) can develop from impurities on ice surfaces and represent a relatively rare biological phenomenon. These ovoid-shaped conglomerations of dirt and moss are only found on some glacier surfaces and provide key habitats for invertebrate colonization. Yet, despite their development and presence being widely reported, no targeted studies of their movement and persistence across years have been conducted. This knowledge gap is particularly important when considering the degree to which glacier moss balls may represent viable, long-term biotic habitats on glaciers, perhaps complete with their own ecological succession dynamics. Here, we describe the movement and persistence of glacier moss balls on the Root Glacier in southcentral Alaska, USA. We show that glacier moss balls move an average of 2.5 cm per day in herd-like fashion, and their movements are positively correlated with glacier ablation. Surprisingly, the dominant moss ball movement direction does not align with the prevailing wind or downslope directions, nor with any dominant direction of solar radiation. After attaining a mature size, glacier moss balls persist for many years, likely in excess of 6 years. Finally, we observed moss ball formation on the Root Glacier to occur within a narrow, low albedo stripe downwind of a nunatuk, a potential key source of moss spores and/or fine-grained sediment that interact to promote their formation.

Characterizing the first wave of fish and invertebrate colonization on a new offshore petroleum platform

Offshore Oil & Gas (O&G) infrastructure creates artificial reef complexes that support marine communities in oceans. No studies have characterized the first wave of colonization, which can reveal information about habitat attraction and ecological connectivity. Here we used opportunistically-collected industrial Remotely Operated Vehicles (ROVs) to investigate fish and invertebrate colonization on a new North Sea O&G platform and trenching of an associated pipeline. We observed rapid colonization of fish communities, with increases in species richness (S), abundance (N), and diversity (H′) over the first four days (the entire study period). By contrast, there was minimal change in motile invertebrate communities over the survey period. After trenching, invertebrate S, N and H′ decreased significantly, whilst fish S, N and H′ increased. This study is the first to report on the pioneer wave of fish and invertebrate colonization on O&G infrastructure, thereby providing rare insight into formation of new reef communities in the sea. These short and opportunistic data are valuable in terms of showing what can be discovered from analysis of ‘pre-installation’ ROV footage of O&G structures, of which there are terabytes of data held by O&G companies waiting to be analyzed by environmental scientists.

Invertebrate Colonization During Leaf Decomposition of Eichhornia azurea (Swartz) Kunth (Commelinales: Pontoderiaceae) and Salvinia auriculata Aubl. (Salvinales: Salvinaceae) in a Neotropical Lentic System

The decomposition of macrophytes is an essential process for cycling of carbon and nutrients, and it is source of organic matter for invertebrates in lakes. We evaluated the colonization by aquatic invertebrates in decomposing leaves of two species of macrophytes in a Neotropical lentic system. The experiment was conducted from November 2007 to February 2008, with the use of 54 litter bags (Eichhornia azurea (Swartz): n = 27 and Salvinia auriculata Aubl.: n= 27), each containing 10 g of dry leaves. Three bags of each species were retrieved after 2, 4, 8, 12, 24, 36, 48, 60 and 72 days of incubation. The remaining leaf mass of the two macrophytes species tended to decrease with time, although at different rates. The decomposition of E. azurea and S. auriculata leaves were classified as rapid and intermediate, respectively. In general, during the experiment carbon: nitrogen ratio declined in E. azurea and increased in S. auriculata, and presented difference among the days of the experiment and between the macrophyte species. In E. azurea mass loss was negatively correlated with carbon: nitrogen ratio of the leaves, but the same pattern was not observed for the S. auriculata leaves. The composition and richness of invertebrates differed among days, but not between macrophytes species. We concluded that the succession process along the detritus chain was more important in structuring the invertebrate community than the variation in the nutritional quality of the leaf litter for these two species of macrophytes.Colonização por Invertebrados Durante a Decomposição foliar de Eichhornia azurea (Swartz) Kunth (Commelinales: Pontoderiaceae) e Salvinia auriculata Aubl. (Salvinales: Salvinaceae) em um Sistema Lêntico NeotropicalResumo. A decomposição de macrófitas é um processo essencial para ciclagem de carbono e nutrientes, e é fonte de matéria orgânica para invertebrados em lagos. Avaliamos a colonização por invertebrados aquáticos em folhas em decomposição de duas espécies de macrófitas em um sistema lêntico Neotropical. O experimento foi conduzido entre novembro de 2007 e fevereiro de 2008, com a utilização de 54 sacos de detrito (Eichhornia azurea (Swartz): n = 27 e Salvinia auriculata Aubl.: n = 27), cada um contendo 10 g de folhas secas. Três sacos de cada espécie foram recuperados após 2, 4, 8, 12, 24, 36, 48, 60 e 72 dias de incubação. A massa remanescente de folha das duas espécies de macrófitas tendeu a diminuir com o tempo, embora a velocidades diferentes. A decomposição de folhas de E. azurea e S. auriculata foram classificadas como rápida e intermédia, respectivamente. Em geral, durante o experimento a razão carbono: nitrogênio diminuiu em E. azurea e aumentou em S. auriculata, e apresentou diferença entre os dias de experimento e entre as espécies de macrófitas. Em E. azurea perda de massa foi negativamente correlacionada com a razão de carbono: nitrogênio das folhas, mas o mesmo padrão não foi observado para as folhas de S. auriculata. A composição e riqueza de invertebrados diferiram entre os dias, mas não entre espécies de macrófitas. Concluímos que o processo de sucessão ao longo da cadeia de detritos foi mais importante na estruturação da comunidade de invertebrados do que a variação na qualidade nutricional do detrito de folha para estas duas espécies de macrófitas.

Influence of antifouling paint on freshwater invertebrates (Mytilidae, Chironomidae and Naididae): density, richness and composition

We conducted a study about invertebrates on artificial substrates with different antifouling paints in order to answer the following questions 1) is there lower accumulation of organic matter on substrates with antifouling paints, 2) is invertebrate colonization influenced by the release of biocides from antifouling paints, 3) is the colonization of aquatic invertebrates positively influenced by the material accumulated upon the substrate surface and 4) is the assemblage composition of invertebrates similar among the different antifouling paints? To answer these questions, four structures were installed in the Baía River in February 1st, 2007. Each structure was composed of 7 wood boards: 5 boards painted with each type of antifouling paints (T1, T2, T3, T4 and T5), one painted only with the primer (Pr) and the other without any paint (Cn). After 365 days, we observed a greater accumulation of organic matter in the substrates with T2 and T3 paint coatings. Limnoperna fortunei was recorded in all tested paints, with higher densities in the control, primer, T2 and T3. The colonization of Chironomidae and Naididae on the substrate was positively influenced by L. fortunei density. The non-metric multidimensional scaling (NMDS) of the invertebrate community provided evidence of the clear distinction of invertebrate assemblages among the paints. Paints T2 and T3 were the most similar to the control and primer. Our results suggest that antifouling paints applied on substrates hinder invertebrate colonization by decreasing the density and richness of invertebrates.