Dean W. Blinn

SELECTED PUBLICATIONS SINCE 1970

• Blinn, D.W. & J.R. Stein. 1970.  Distribution and taxonomic reappraisal of Ctenocladus (Chlorophyceae: Chaetophorales).  Journal of Phycology 6:101-105.

• Blinn, D.W. 1971. Autecology of Ctenocladus circinnatus Borzi (Chlorophyceae) in saline environments. Canadian Journal of Botany 49:735-743.

• Blinn, D.W. & K. Button. 1973. The effect of temperature on parasitism of Pandorina sp. by Dangeardia mammillata B. Schröder in an Arizona mountain lake. Journal of Phycology 9:323-326.

• Blinn, D.W. & E. Morrison. 1974. Intercellular cytoplasmic connections in Ctenocladus circinnatus Borzi with possible ecological significance. Phycologia 13:95-97.

• Stewart, A. & D.W. Blinn. 1976. Studies on Lake Powell, USA: Environmental factors influencing phytoplankton success in a high desert warm monomictic lake. Archiv. für Hydrobiologie 78:139-164.

• Tompkins, T. & D.W. Blinn. 1976. The effect of mercury on the growth rate of Fragilaria crotonensis Kitton and Asterionella formosa Hass. Hydrobiologia 49:111-116.

• Czarnecki, D. & D.W. Blinn. 1977. Diatoms of lower Lake Powell and vicinity. Diatoms of Southwestern USA. Bibliotheca Phycologia 28:1-119 pp.

• Czarnecki, D. & D.W. Blinn. 1978. Diatoms of the Colorado River in Grand Canyon National Park and vicinity. Diatoms of Southwestern USA. Bibliotheca Phycologia 38:1-182.

• Czarnecki, D. & D.W. Blinn. 1978. Observations of southwestern diatoms. I. Plagiotropis Arizonica n. sp. (Bacillariophyta, Entomoneidaceae), a large mesohalobous diatom. Transactions American Microscopical Society 98:102-106.

• Hoham, R. & D.W. Blinn. 1979. Distribution of cryophilic algae in an arid region, the American Southwest. Phycologia 18:133-145.

• Tuchman, M. & D.W. Blinn. 1979. Comparison of attached algal communities on natural and artificial substrata along a thermal gradient. British Phycological Journal 14:243-254.

• Hamala, J., S. Duncan, & D.W. Blinn. 1980. A portable pump sampler for lotic periphyton. Hydrobiologia 80:189-191.

• Czarnecki, D., D.W. Blinn, & N. Grim. 1980. Aspects of valve morphology in Plagiotropis arizonica, a diatom with an imperforate siliceous covering. Transactions American Microscopical Society 99:445-447.

• Blinn, D.W., A. Fredericksen, & V. Korte. 1980. Diatom community structure on three different rock substrata in a lotic system. British Phycological Journal 15:303-310.

• Schwartz, S., D.W. Blinn, & G. Johnson. 1981. The physico-chemical and planktonic response of a simazine-treated shallow mountain lake. Internationale Revue der Gestamen Hydrobiologia 66:249-262.

• Blinn, D.W., C. Pinney, & M.W. Sanderson. 1982. Nocturnal planktonic behavior of Ranatra montezuma Polhemus (Nepidae: Hemiptera) in Montezuma Well, Arizona. Journal of Kansas Entomological Society 55:481-484.

• Blinn, D.W. & D.B. Johnson. 1982. Filter-feeding of Hyalella montezuma, an unusual behavior for a freshwater amphipod. Freshwater Invertebrate Biology 1:48-52.

• Korte, V. & D.W. Blinn. 1983. Diatom colonization on artificial substrata in pool and riffle zones studied by light and scanning electron microscopy. Journal Phycology 19:332-341.

• Boucher, P., D.W. Blinn, & D.B. Johnson. 1984. Phytoplankton ecology in an unusually stable environment (Montezuma Well, Arizona, U.S.A.). Hydrobiologia 119:149-160.

• Blinn, D.W. & J. Green. 1986. A pump sampler study of micro-distribution in Walker Lake, Arizona, U.S.A.: a senescent crater lake. Freshwater Biology 16:175-185.

• Blinn, D.W., V.T. Wagner, & J.N. Grim. 1986. Surface sensilla on the predaceous fresh-water leech, Erpobdella montezuma: Possible importance in feeding. Transactions of the American Microscopical Society 105:21-30.

• Blinn, D.W. 1986. Pros and cons of artificial versus natural substrata, pp. 776-781, In: M. Ricard, (Ed.), Diatoms as indicators of pollution. Proceedings of the 8th International Diatom Symposium. Paris, France. 1984.

• Wagner, V.T. & D.W. Blinn. 1987. A comparative study of the maxillary setae for two coexisting species of Hyalella (Amphipoda), a filter feeder and a detritus feeder. Archiv. für Hydrobiologia 109:409-419.

• Colletti, P.J., D.W. Blinn, A. Pickart, & V.T. Wagner. 1987. Influence of different densities of the mayfly grazer Heptagenia criddlei on lotic diatom communities. Journal of the North American Benthological Society 6:270-280.

• Blinn, D.W., R.W., Davies, & B. Dehdashti. 1987. Specialized pelagic feeding by Erpobdella montezuma (Hirudineae). Holarctic Ecology 10:235-240.

• Davies, R. W., D.W. Blinn, B. Dehdashti, & R.N. Singhal. 1988. The comparative ecology of three species of Erpobdellidae (Annelida: Hirudinoidea). Archiv. für Hydrobiologie 111:601-614.

• Blinn, D.W., C. Pinney, & V.T. Wagner. 1988. Intraspecific discrimination of amphipod prey by a freshwater leech through mechanoreception. Canadian Journal of Zoology 66:427-430.

• Blinn, D.W., N.E. Grossnickle, & B. Dehdashti. 1988. Diel vertical migration of a pelagic amphipod in the absence of fish predation. Hydrobiologia 160:165-171.

• Blinn, D.W., R.E. Truitt, & A. Pickart. 1989. Feeding ecology and radular morphology of the freshwater limpet Ferrissia fragilis. Journal of the North American Benthological Society 8:237-242.

• Blinn, D.W. & C. Runck. 1989. Substratum requirements for oviposition, seasonal egg densities and conditions for egg eclosion in Ranatra montezuma Polhemus (Heteroptera: Nepidae). Annals of the Entomological Society of America 82:707-711.

• Blinn, D.W., R. Truitt, & A. Pickart. 1989. Response of epiphytic diatom communities from the tailwaters of Glen Canyon Dam, Arizona, to elevated water temperature. Regulated Rivers 4:91-96.

• Blinn, D.W. & M. Sanderson. 1989. Aquatic insects in Montezuma Well, Arizona, USA: a travertine spring mound with high alkalinity and dissolved carbon dioxide. Great Basin Naturalist 49:85-88.

• Blinn, D.W. & R.W. Davies. 1989. The evolutionary importance of mechanoreception in three erpobdellid leech species. Oecologia 79:6-9.

• Blinn, D.W., S.L. Blinn, & I.A.E. Bayly. 1989. The feeding ecology of Haloniscus searlei Chilton, an oniscoid isopod living in athalassic saline waters. Australian Journal of Marine and Freshwater Research 40:295-301.

• Blinn, D.W. & R.W. Davies. 1989. New distributional records for leeches (Hirudinoidea) in Arizona. Southwestern Naturalist 34:431-432.

• Duncan, S.W. & D.W. Blinn. 1989. Importance of physical variables on the seasonal dynamics of epilithic algae in a highly shaded canyon stream. Journal of Phycology 25:455-461.

• Blinn, D.W., B. Dehdashti, C. Runck, & R.W. Davies. 1990. The importance of prey size and density in an endemic predator-prey couple (leech) Erpobdella montezuma amphipod Hyalella montezuma. Journal of Animal Ecology 59:187-192.

• Usher, H.D., and D.W. Blinn. 1990.  Influence of various exposure periods on the biomass and chlorophyll aof Cladophora glomerata (Chlorophyta).  Journal of Phycology 26:244-249.

• Runck, C. and D.W. Blinn. 1990.  Population dynamics and secondary production by Ranatra montezuma (Heteroptera: Nepidae). Journal of the North American Benthological Society 9:262-270.

• Blinn, D.W. and R.W. Davies. 1990.  Concomitant diel vertical migration of a predatory leech and its amphipod prey. Freshwater Biology 24:401-407.

• Blinn, D.W. and G.A. Cole. 1991.  Algae and invertebrate biota in the Colorado River: Comparison of pre- and post-dam conditions, pp. 85-104.  In: National Research Council (Eds).  Colorado River Ecology and Dam Management.  National Academy of Science Press, Washington, D.C.  238 pp.

• Dehdashti, B. and D.W. Blinn. 1991.  Population dynamics and production of the pelagic amphipod, Hyalella montezuma in a thermally constant system.  Freshwater Biology 25:131-141.

• Blinn, D.W. 1991.  The diatom flora of Lake Eyre South:  A large episodically filled salt lake in South Australia.  Hydrobiologia 210:101-104.

• Tudor, E.R., D.W. Blinn, and D.M. Churchill.  1991.  Distribution of diatoms in the northern Kimberley Region, Western Australia in relation to water chemistry.  Journal of the Royal Society of Western Australia 73:93-99.

• Hardwick, G.G., D.W. Blinn, and H.D. Usher. 1992.  Epiphytic diatoms on Cladophora glomeratain the Colorado River, Arizona: Longitudinal and vertical distribution in a regulated river.  Southwestern Naturalist 37:148-156.

• Runck, C. and D.W. Blinn. 1992.  Foraging ecology of Ranatra montezuma (Heteroptera): an optimal forager in Montezuma Well, Arizona.   Issue 2.  Limnology and Aquatic Biology of the Southwest.  Journal of the Arizona-Nevada Academy of Science 26:119-129.

• Blinn, D.W., C. Runck, D.A. Clark, and J.N. Rinne. 1993.   Effects of rainbow trout predation on Little Colorado spinedace. Transactionsof the American Fisheries Society 122:139-143.

• Blinn, D.W., C. Runck, and R.W. Davies.  1993.  The impact of prey behaviour and prey density on the foraging ecology of Ranatra montezuma (Heteroptera): a serological examination.  Canadian Journal of Zoology 71:387-391.

• Thomas, P., D.W. Blinn, and P. Keim. 1994.  A test of an allopatric speciation model for congeneric amphipods in an isolated aquatic ecosystem.  Journal of the North American Benthological Society 3:100-109.

• Kalarani, V., D.C. Reddy, D.W. Blinn, and R.W. Davies. 1993.  Interspecific differences in respiration and energy storage reserves in two freshwater predatory leeches from ecosystems of contrasting stability.  Comparative Biochemistry and Physiology 104A:239-242.

• Blinn, D.W. 1993.  Diatom community structure along physicochemical gradients in saline lakes.  Ecology 74:1246-1263.

• Runck, C. and D.W. Blinn. 1993.  Seasonal diet of a threatened native cyprinid in the American Southwest: Lepidomeda vittata Southwestern Naturalist 38:157-159.

• Runck, C. and D.W. Blinn. 1993.  Secondary productivity by Telebasis salva (Odonata) in a thermally constant aquatic ecosystem. Journal of the North American Benthological Society 12:136-147.

• Shannon, J.P., D.W. Blinn, and L.E. Stevens. 1994.  The role of trophic interactions in structuring lotic benthic communities. Freshwater Biology 31:213-220.

• Blinn, D.W., R.H. Hevly, and O.K. Davis. 1994.  Continuous Holocene record of diatom stratigraphy, paleohydrology, and anthropogenic activity in a spring-mound in southwestern United States.  Quaternary Research 42:197-205.

• Runck, C. and D.W. Blinn. 1994.  Role of Belostoma bakeri (Heteroptera) in the trophic ecology of a fishless desert spring. Limnology and Oceanography 39:1800-1812.

• Blinn, D.W., J.P. Shannon, and L.E. Stevens, and J.P. Carder. 1995.  Consequences of fluctuating discharge for lotic communities. Journal of the North American Benthological Society 14:233-248.

• Govedich, F., G. Oberlin, and D.W. Blinn. 1996.  Comparison of channel and hyporheic invertebrate communities in a Southwestern USA desert stream.  Journal of Freshwater Ecology 11:201-209.

• Shannon, J.P., D.W. Blinn, P.L. Benenati, and K.P. Wilson. 1996.  Organic drift in a regulated desert river.  Canadian Journal of Fisheries and Aquatic Sciences 53:1360-1369.

• Oberlin, G. E. and D. W. Blinn. 1997.  The effect of temperature on the metabolism and behavior of an endemic amphipod, Hyalella montezuma from Montezuma Well. Freshwater Biology 37:55-59.

• Thomas, P. E., D. W. Blinn, and P. Keim. 1997.  Genetic and behavioural divergence among desert spring amphipod populations. Freshwater Biology 38:137-43.

• Minckley, T. A., O. K. Davis, D. Eastoe, V. Haynes, D. W. Blinn. 1997.  Preliminary analysis of environmental indicators from a Mastodon site in the Prescott National Forest, Yavapai County.  Arizona-Nevada Academy of Science 30:23-29.

• Shaver, M. L., J. P. Shannon, K. P. Wilson, P. L. Benenati, and D. W. Blinn. 1997.  Effects of suspended sediment and desiccation on the benthic tailwater community in the Colorado River, USA.  Hydrobiologia 357:63-72.

• Drost, C.A. and D.W. Blinn. 1997.  Invertebrate community of Roaring Springs Cave, Grand Canyon National Park, Arizona. Southwestern Naturalist 42:497-500.

• Stevens, L. E., J.P. Shannon, and D. W. Blinn. 1997.  Colorado River Benthic ecology in Grand Canyon Arizona, USA: dam, tributary, and geomorphic influences.  Regulated Rivers 13:129-149.

• Blinn, D.W., J.P. Shannon. P.L. Benenati, and K.P. Wilson. 1998.  Algal ecology in tailwater stream communities: Colorado River below Glen Canyon Dam, Arizona.  Journal of Phycology 34:734-740.

• Herbst, D.B. and D.W. Blinn. 1998.  Experimental mesocosm studies of salinity effects on the benthic algal community of a saline lake.  Journal of Phycology 34:772-778.

• Benenati, P.L., J.P. Shannon, and D.W. Blinn. 1998.  Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry, Arizona, USA. Regulated Rivers 4:519-532.

• Thomas, E.P., D.W. Blinn, and P. Keim. 1998.  Do xeric landscapes increase genetic divergence in aquatic ecosystems? Freshwater Biology 40:587-593.

• Blinn, D.W., J. White, T. Pradetto, and J. O'Brien. 1998.  Reproductive ecology and growth of a captive population of Little Colorado spinedace (Lepidomeda vittata: Cyprinidae).  Copeia 998:1010-1015.

• Blinn, D.W., J.P. Shannon. K.P. Wilson, C. O'Brien, and P.L. Benenati. 1998.  Response of benthos and organic drift to a controlled flood, pp 259-271, in Webb, R.H., Schmidt, J.C., Marzolf, G.R. and Valdez, R.A.   The Controlled Flood in Grand Canyon. Washington D.C.  American Geophysical Union.   Geophysical Monograph 110.  367 pp.

• Valdez, R.A., J.P. Shannon, and D.W. Blinn. 1998.  Biological implications of the 1996 controlled flood, pp 343-350.  In: Webb, R.H., Schmidt,  J.C., Marzolf, G.R.and Valdez, R.A. The Controlled Flood in Grand Canyon.Washington D.C.  American Geophysical Union. Geophysical Monograph 110.  367 pp.

• Oberlin, G.E., J.P. Shannon, and D.W. Blinn. 1998.  Watershed influence on the macroinvertebrate fauna of ten major tributaries of the Colorado River through Grand Canyon, Arizona. Southwestern Naturalist 44:17-30.

• Wilson, K.P., J.P. Shannon, D.W. Blinn. 1998.  Effects of suspended sediments on biomass and cell morphology of Cladophora glomerata (Chlorophyta) in the Colorado River, Arizona.  Journal of Phycology 35:35-41.

• Govedich, F.R., D.W. Blinn. P. Keim, and R.W. Davies. 1998.  Phylogenetic relationships of three genera of Erpobdellidae (Hirudinoidea), with a description of a new genus (Motobdella) and species, M. sedonensis.  Canadian Journal of Zoology 76:2164-2171.

• McLoughlin, N.J., D.W. Blinn, and R.W. Davies. 1999.  An energetic evaluation of a predator (leech)- prey (amphipod) couple in Montezuma Well, Arizona.  Functional Ecology 13:45-50.

• Govedich, F.R., D.W. Blinn, R.H. Hevly, and P.S. Keim. 1999.  Cryptic radiation in erpobdellid leeches in xeric landscapes:  A molecular analysis of population differentiation. Canadian Journal of  Zoology. 77:52-57.

• Haden, G.A., D.W. Blinn, J.P. Shannon, and K.P. Wilson. 1999.  Driftwood: An alternative habitat for macroinvertebrates in a large desert river.  Hydrobiologia 397:179-186.

• Haden, G.A., D.W. Blinn, J.P. Shannon, and K.P. Wilson. 1999.  Interference competition between the net-building caddisfly Ceratopsyche oslari and the amphipod Gammarus lacustris.  Journal of Freshwater Ecology 4:277-280. 

• O’Brien, C. and D.W. Blinn. 1999.  The endemic spring snail Pyrgulopsis montezumensis in a high CO2 environment: Importance of extreme chemical habitats as refugia.  Freshwater Biology 42:225-234.

• Wetzel, M.J., G.E. Oberlin, and D.W. Blinn. 1999.  Aquatic Oligochaeta (Annelida: Clitellata) of Montezuma Well, Arizona: A near-thermally constant limnocrene. Southwestern Naturalist 44:514-518.

• Pomeroy, K.E., J.P. Shannon, and D.W. Blinn. 2000.  Leaf breakdown in a regulated desert river: Colorado River, Arizona USA.  Hydrobiologia 434:193-199. 

• Shepard, W.D., D.W. Blinn, R. J. Hoffman, and P.T. Kantz.  2000.  The algae of Devils Hole, Nevada, Death Valley National Park.  Western North American Naturalist 60:410-419.

• Benenati, E.P., J.P. Shannon. D.W. Blinn, K.P. Wilson, and S. J. Hueftle.  2000.  Reservoir-River linkages:  Lake Powell and the Colorado River, Arizona.  Journal of the North American Benthological Society 19:742-755. 

• Shannon, J.P., D.W. Blinn, T. McKinney, P.L. Benenati, K.P. Wilson, and C.O. O'Brien. 2001. Aquatic food base response to the 1996 test flood below Glen Canyon Dam: Colorado River, Arizona.  Ecological Applications 11:672-685.

• Benenati, E.P., J.P. Shannon, J.S. Hagen, and D.W. Blinn.  2001.  Drifting fine particulate organic matter below Glen Canyon Dam in the Colorado River, Arizona.  Journal of Freshwater Ecology 16:235-244.

• Shannon, J.P., D.W. Blinn, G.A. Haden, E.P. Benenati, and K.P. Wilson.  2001.  Food web implications of 13C and 15N variability over 370 km of the regulated Colorado River, USA.  Isotopes in Environmental Health Studies 37:179-191.

•  Blinn, D.W. and P.C.E. Bailey.  2001.  Land use influence on stream water quality and diatom communities in Victoria, Australia: a response to secondary salinization.  7^th International Salt Lake Symposium.  Hydrobiologia 466:231-244.

• Miller, M.P., D.W. Blinn, and P. Keim.  2002.  Correlations between observed dispersal capabilities and patterns of genetic differentiation in populations of four aquatic insect species from the Arizona White Mountains, USA.  Freshwater Biology 47:1660-1673.

• O’Brien, C., D.W. Blinn, and C. van Riper III. 2002.  Waterfowl, acanthocephalans, and amphipods in Montezuma Well, Arizona-  what is the role of a parasite? U.S.G.S. Research Brief:  20 November 2002.

• Compton-O’Brien, A., R.D. Foust, Jr., F.E. Ketterer, and D.W. Blinn.  2003.  Total arsenic in a fishless desert spring:  Montezuma Well, Arizona.  American Chemical Society Symposium “Biochemistry of Environmentally Important Trace Elements”.  ACS Series 835.  Chapter 15, pp 200-209.

• Witt, J.D.S., D.W. Blinn, and P.D.N. Hebert.  2003.  The recent evolutionary origin of the ecologically novel amphipod Hyalella montezuma offers an ecological explanation for cryptic speciation.  Molecular Ecology 12:405-413. 

• Rowell, K. and D.W. Blinn.  2003.  Herbivory on a chemically defended plant as a predation deterrent in Hyalella azteca.  Freshwater Biology 48:247-254.

• Haden, G.A., J.P. Shannon, K.P. Wilson, and D.W. Blinn.  2003.  Benthic community structure of the Green and Colorado Rivers through Canyonlands National Park, Utah, USA.  Southwestern Naturalist 48:23-35.

• Ellsworth, P.M. and D.W. Blinn.  2003.  Distribution and biomass of Tropocyclops prasinus mexicanus (Cyclopoida) in a near-thermally constant environment, Montezuma Well, Arizona.   Southwestern Naturalist 48:341-346.

• Earl, S. and D.W. Blinn.  2003. Effects of wildfire ash on water chemistry and biota in southwestern USA streams.  Freshwater Biology 48:1015-1030.

• Blinn, D.W., S.A. Halse, A.M. Pinder, R.J. Shiel, and J.M. McRae. 2004. Diatom and micro-invertebrate communities and environmental determinants in the western Australian wheatbelt: A response to salinization. Hydrobiologia 528: 229.248.

• Blinn, D.W. and D.W. Ruiter. 2005. Caddisfly (Trichoptera) community structure and distribution in Arizona, USA: Effects of selected environmental determinants. Proceedings of the 11th International Symposium on Trichoptera (2003, Osaka). Pp 63-71.

• Yard, M.D., G.E. Bennett, S.N. Mietz, L.G. Coggins, Jr., L.E. Stevens, S. Hueftle, and D.W. Blinn. 2005. Influence of topographic complexity on solar insolation estimates for the Colorado River. Ecological Modelling 183:157-172.

• Blinn, D.W. and N.L. Poff. 2005. Chapter 11. Colorado River Basin. In: A. Benke and C.E. Cushing (eds.). Rivers of North America. Academic Press. Pp. 483-538.

• Bailey, P.C.E., P.I. Boon, D.W. Blinn, and W.D. Williams. 2006. Salinisation as an ecological perturbation to rivers, streams and wetland of arid and semi-arid regions. In: R.T. Kinsford (ed.). Chapter 10. Ecology of Desert Rivers. Cambridge University Press. Pp. 280-314.

• Blinn, D.W. and D.E. Ruiter. 2006. Tolerance values of stream caddisflies (Trichopteran) in the lower Colorado River Basin, USA. Southwestern Naturalist 51:326-337.

• Athens, J.S., J.V. Ward, and D.W. Blinn. 2007. Vegetation history of Laysan Island. Northwestern Hawaiian Islands. Pacific Science 61:17-37.

• Wilson, K.P. and D.W. Blinn. 2007. Food web structure: energetics, and importance of allochthonous carbon in a desert cavernous limnocrene: Devils Hole, Nevada. Western North American Naturalist 67:185:198.

• Doucett, R.R., J.C. Marks, D.W. Blinn, M. Caron, and B.A. Hungate. 2007. Measuring terrestrial subsidies to aquatic food webs using stable isotopes of hydrogen. Ecology 68:1587-1592.

• Blinn, D.W. 2008. The extreme environment, trophic structure, and ecosystem dynamics of a large, fishless desert spring. In: L. Stevens and V. Meretsky (eds.). Chapter 6. Aridland Springs in North America. University of Arizona Press. Pp. 98-126.

• Blinn, D,W, D,E, Ruiter. and O.S. Flint. 2009. Notes on a collection of caddisflies (Trichoptera) from Carroll county Iowa (U.S.A.). Proceedings of the Entomological Society of Washington 111:151-158.

• James, K.R., B.T. Hart, P.C.E. Bailey, and D.W. Blinn. 2009. Impact of secondary salinisation on freshwater ecosystems: effect of experimentally increased salinity on an intermittent floodplain wetland. Marine and Freshwater Research 60:246-258.

• Blinn, D.W. and D.E. Ruiter. 2009. Phenology and distribution of caddisflies (Trichoptera) in Oak Creek, a high-desert perennial stream in Arizona. Southwestern Naturalist 54:182-194.

• Blinn, D.W. and D.E. Ruiter. 2009. Caddisfly (Trichoptera) assemblages along major river drainages in Arizona. Western North American Naturalist 69:299-308.

• Blinn, D.W. Life Beneath the Water Surface in Montezuma Well, Arizona. Submitted.

Updated 02/09/2011 11:55 AM